3)5" bs jtf 3^5 \ 4 -V- Cornell University Library QE 862.D5P2516 The osteology of the trachodont dinosaur 3 1924 004 594 895 CORNELL UNIVERSITY LIBRARY o < ■o Hi UNIVERSITY OFvTORONTO STUDIES GEOLOGICAL SERIES No. 11: THE OSTEOLOGY OF THE TRACHODONT DINOSAUR KRITOSAURUS INCURVIMANUS, by W. A. Parks THE UNIVERSITY LIBRARY: PUBLISHED BY THE LIBRARIAN, 1920 TflmversitE of Toronto Stuotes COMMITTEE OF MANAGEMENT Chairman: Sir Robert Alexander Falconer, LL.D., K.C.M.G. President of the University Professor W. J. Alexander, Ph.D. Professor J. J. Mackenzie, B.A., M.B. Professor J. P. McMurrich, Ph.D. Brig.-Gen. C. H. Mitchell, B.A.Sc, C.B.,C.M.G., D.S.O. Professor G. H. Needler, Ph.D. Professor George M. Wrong, M.A. General Editor: H. H. Langton, M.A. Librarian of the University THE OSTEOLOGY OF THE TRACHODONT DINOSAUR KRITOSAURUS INCURVIMANUS BY WILLIAM A. PARKS, Ph.D., F.RS.C. PROFESSOR OF PALAEONTOLOGY UNIVERSITY OF TORONTO / {Jf*/**? TABLE OF CONTENTS PAGE Discovery 5 General Description ... 7 Detailed Description 11 Head 11 Vertebral Column 23 Shoulder Girdle and Fore Limbs 31 Ribs and Sternal Bones 44 Pelvic Girdle and Hind Limbs '. 47 Musculature 63 Integument 72 Cornell University Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924004594895 THE OSTEOLOGY OF THE TRACHODONT DINOSAUR KRITOSAURUS INCURVIMANUS 1 Discovery In the summer of 191 8 the Royal Ontario Museum of Palaeontology organized an expedition to search for dinosaur- ian remains in the well known and prolific locality on the Red Deer river in southern Alberta. The party was fortunate in the discovery of the skeleton of a crestless trachodont dinosaur, which, on being removed from the matrix, has revealed characteristics of sufficient interest to warrant a somewhat detailed description. The specimen was obtained from the beds of the Belly River formation in the bad lands of the Red Deer river which are most conspicuously developed in the vicinity of the confluence of Sand Hill creek with the main stream. The skeleton lay at an elevation of 116 feet (aneroid) above the river at a point about two and a half miles above Happy Jack ferry and a mile south of the river. §f #■ The animal fell or was washed by the waves on a sloping shore of sand which had a general trend of N.30°W.$>i|This old shore is now represented by a bed of sandstone con- taining numerous hard concretions of clay ironstone. ,,» The body was extended in a general direction of N.3°W.'| I, with the limbs towards the water, i.e., north-easterly. Waves from the open sea very rapidly buried the skeleton in white sand which has become an extremely hard sandstone showing pronounced cross bedding which dips 30°N.6o°E. ') ijSo ^ritosaurus incurvimanus, Parks, Transactions Royal Society of Canada, Third Series, Vol. XIII, Sect. IV, 1919. 6 Kritosaurus incurvimanus rapid was the entombment that the collapse of the trunk was prevented, the ribs of the two sides and the two sternal bones being embedded in normal position. The bones of the right or under fore limb also lay in normal position with the palmar surface of the manus upwards ; the right or upper limb had so sagged at the elbow that the radius and ulna occupied a position at 70° to the horizontal, with the manus, also with the palmar surface upwards, lying on the sub- stratum at the same level with its fellow. Some disturbance of the bones of the hind limbs was brought about by the action of waves before entombment was effected, the left fibula together with some of the meta- tarsals and phalanges being washed a short distance out. The right limb was less disturbed, only the bones of the pes being somewhat scattered. Since the time of entombment the sandstone has become very hard, almost flinty in places, and a thin film of clay ironstone has formed over the surface of some of the bones. At the time of discovery natural erosion had removed the overlying rock, bringing about the exposure of the head, scapula, femur, ilium, ribs, and transverse processes of the vertebrae. The exposed parts were, of necessity, injured, but a more serious loss was occasioned by two small water- ways, one of which had entirely removed the anterior bones of the head and the other had cut off the extremity of the tail. Despite these imperfections the skeleton retains nearly every feature required for detailed description, the posterior caudal vertebrae being of slight anatomical significance. Owing to the hardness and shattered condition of the rock and the great thickness of the blocks, the specimen was unusually difficult to excavate and required two years' preparation in the laboratory. As the upper or left side was seriously injured it was decided to prepare the specimen as a panel mount showing the right or under side. Before pro- ceeding with this operation the head, scapula, coracoid, and limb bones of the left side were entirely removed from the matrix; in the final preparation these bones were replaced, as far as possible, in natural position. General Description Lawrence M. Lambe described a crestless trachodont from the Belly river formation as Gryposaurus notdbilis. The type of this genus and species is in the Victoria Memorial Museum, Ottawa. The head has been prepared but the partially preserved body is in very hard ironstone matrix from which it will be difficult or impossible to remove it. Lambe's description of the genus is as follows: "Skull large, narrow and very deep, with highly arched nasals. The lower, anterior border of the premaxillae expanded laterally. Orbit much smaller than the lateral temporal fossa. Quad- rate high, partially separated from the jugal by a small quadrato-jugal. Mandible robust. Predentary expanded laterally and deflected in its hinder half, and posteriorly bifurcated below at the midline. Neural spines of the anterior dorsal vertebrae long. Ischia not expanded distally. Body covered with small, polygonal, non-imbricating, tuber- culate scales of rather uniform size. 1 In general appearance and in all essentials which can be compared the specimen under review so closely resembles Lambe's type that there can be no doubt as to the generic identity of the two individuals. In species as well as in genus our specimen shows a marked resemblance to Lambe's type; there are, however, several points of difference which seem to indicate a separate species. In view of the considerable degree of variation known to occur in individuals of the same species of dinosaur, the present detailed description would scarcely be justified for the sole purpose of erecting a new and somewhat doubt- ful species, but, as the body of the genus has not hitherto been described, and as the specimen shows practically all anatomical features in excellent detail, the description seems to be warranted for generic differentiation alone. In addition to its very strong resemblance to Gryposaurus notabilis the specimen has striking affinities with Kritosaurus novajovius from the Cretaceous beds of Ojo Alamo in New Ottawa Naturalist, Vol. XXVII, No. n, February, 1914. 7 8 Kritosaurus incurvimanus Mexico. This form was described by Barnum Brown in 1 910, both genus and species being founded on an imperfect head in which the nasal bones were absent. The generic description follows: "Skull deep; muzzle narrow; frontals short, orbital portion reduced, barely coming to the border of the orbit; nasals and premaxillaries very long; quadrate elongate; quadrato-jugal short antero-posteriorly, completely separat- ing quadrate and jugal ; mandibular rami massive, edentulous portion decurved; teeth spatulate in lower jaw." 1 Brown's specific account is of no immediate interest as our specimen is evidently distinct and much more closely related to Gryposaurus notabilis. Brown maintains that Gryposaurus and Kritosaurus are identical and this view has been adopted by Gilmore, who has prepared a model of the head of Kritosaurus in which the arched nasals of Lambe's type are incorporated. Owing to the loss of the determinative bones in the anterior part of the head our specimen fails to be of value in differentiating the two genera; in fact, the only means of decision is the dis- covery of a more perfect example of Kritosaurus novajovius. As far as the preserved parts are concerned I should have no hesitation in ascribing our species to either genus and as Kritosaurus has priority that generic name is used. Should further investigation show that the genera are distinct, the greater resemblance to Lambe's type would necessitate the removal of our species to Gryposaurus.- Lambe objects strongly and with very good reason to the use of Trachodon as a generic name and, consequently, to that of Trachodontidae as a family designation. He prefers to found the family on Leidy's genus Hadrosaurus as proposed by Cope in 1869, whereas Trachodontidae was introduced by Lydekker in 1888. The genus Trachodon was founded on a single mandibular tooth but Hadrosaurus rests on far more extensive material. Lambe, therefore, gives the following 'Bull. Am. Mus. Nat. Hist., Vol. XXVIII, Art. XXIV, 1910. 2 After the examination of a photograph Mr. Brown has assured me that the specimen is undoubtedly an example of his genus. General Description 9 classification of the family, enumerating the genera in which the structure of the head is fairly well known : FAMILY HADROSAURIDAE Sub-Family Hadrosaurinae Sub-Family Saurolophinae Gryposaurus, Lambe, Belly River Stephanosaurus, Lambe, Belly River Edmontosaurus, Lambe, Edmonton Prosaurolophus, Brown, Belly River Kritosaurus, Brown, Uncertain horizon Corythosaurus, Brown, Belly River Claosaurus, Marsh, Lance Saurolophus, Brown, Edmonton Diclonius, Cope, Lance Cheneosaurus, Lambe, Edmonton It will be observed that Lambe does not admit the identity of Gryposaurus and Kritosaurus and that "Trachodon" with all its derivatives is eliminated from the nomenclature. Despite Lambe's contention "Trachodon" has not been read out of the literature; in consequence, avoiding all contention, the systematic position of our species may be indicated as follows : Order Dinosauria Sub-order Predentata Family Trachodontidae or Hadrosauridae Sub-family Trachodontinae or Hadrosaurinae Genus Kritosaurus or Gryposaurus It is worthy of note that 'Kritosaurus (Gryposaurus) is the only genus of the Trachodontinae, i.e., crestless trachodonts with non-footed ischia, occurring in a horizon of the Upper Cretaceous as low as the Belly River. Kritosaurus incurvimanus is a typical crestless trachodont with non-footed ischia. It is distinguished by the deep and narrow head with a probable median nasal protuberance, by peculiarities of the integument, by the presence of distinct dermal callosities along the median line of the back, by the possession of two wedge-shaped phalanges in the manus and of four phalanges in the fifth digit, and by peculiarities of the mandibular teeth. It is distinguished from Kritosaurus (Gryposaurus) notabilis by a slight difference in the shape of the orbit, a more anterior position of the nasal prominence, a greater separation of the jugal and quadrate by the quad- Ottawa Naturalist, Vol. XXI, No. n, p. 138, 1918. io Kritosaurus incurvimanus rato-jugal, the failure of an emargination on the anterior edge of the orbit, and by the generally smaller size. The head is approximately 2 feet 3 inches in length; the thirteen cervical vertebrae measure 3 feet 6 inches; the sixteen dorsal vertebrae extend 5 feet 4 inches; the nine sacral vertebrae account for 2 feet 6 inches, and the seventeen caudals (all that are preserved) for 4 feet 2 inches. The total length was probably about 27 feet. The drawing (Plate 1) shows the various parts of the skeleton in the position in which they lay in the quarry except for necessary adjustment in the case of some of the bones of the hind feet. No restora- tion has been attempted beyond the dotting in of bones where required to show the association of others. The photograph (Plate II) shows the skeleton as mounted. The position of the head has been altered, the pose of the limbs slightly changed, and a few missing phalanges of the pes restored. The relationships of the species as indicated by the head have already been briefly reviewed. The skeleton shows closer affinities with Claosaurus annectens than with any other crestless trachodont of which the body has been described. The skeleton of Claosaurus annectens, mounted in the United States National Museum, measures 26 feet 3 inches and the estimated length of our specimen is 27 feet. It may be concluded, therefore, that the animals are of essentially the same size. The fore limb, however, is relatively longer than in C. annectens, the humerus, and radius and ulna being one-fourth greater. In the hind limb the femur is about equal in both species but the tibia and fibula are 1.07 the length of the corresponding bones of C. annectens. The same relationship is observed in the third metatarsal. Despite the greater length of the limbs both the pectoral and pelvic girdles are lighter in our species. The scapula, ilium, and ischium are distinctly shorter but the prepubis is longer, narrower, and of very different shape. Detailed Description Head Plates III and IV The left or exposed side of the head had lost by erosion both temporal arcades, the quadrate, the whole of the anterior end, and most of the squamosal and pterygoid. The quadrato- jugal was found unimpaired lying in the matrix of the orbit, and several fragments of the jugal, maxilla, and dentary were also recovered. The softening of the rock on the upper or left side has made possible the working out of the anatomy of the cranium proper which would have been difficult or even impossible in the extremely hard matrix in which the under side was embedded. The narrow and deep character of the head is indicated in the table of measurements at the close of this section. Making allowance for the smaller size it will be observed that the proportions are very similar to those of Gryposaurus notabilis which are introduced for comparison. The nasals (N) meet on the median line in a clearly marked straight suture; posteriorly they meet the frontals in a more irregular overlapping suture with a marked posterior prong medially. They are bounded laterally by the pre- frontals and infero-laterally by the premaxillaries but they do not meet the lachrymals. The premaxillary overlaps the nasal which extends to some distance below the suture. The superior margin shows a slight concavity from the frontal suture forwards with only the suspicion of an upward tendency at the most anterior part preserved (135 mm. on the median line from the suture with the frontal). This point is a little in advance of the anterior end of the lachrymal. In Gryposaurus notabilis a vertical line in a similar position would cut the nasal prominence rather in front of than behind its maximum height. There can be no doubt that if our specimen possessed a nasal prominence it was situated far in advance of the position occupied by this determinative 11 12 Kritosaurus incurvimanus feature in G. notabilis. It is chiefly on this account that the present species is regarded as distinct. On the lateral aspect of the nasal, 70 mm. in front of the suture with the prefrontal and 45 mm. below the superior margin, there is a small foramen directed inwards, upwards, and backwards. Five millimetres above this opening there is a smaller and less conspicuous foramen. The lachrymal (L) is a small bone forming about half of the anterior border of the orbit ; it is bounded above by the prefrontal, supero-anteriorly by the premaxillary, below for 70 mm. by the jugal posteriorly and for 30 mm. by the maxillary anteriorly. The premaxillary (Pm) is represented only by its posterior end which lies between the lachrymal and the nasal with a broadly overlapping suture on the latter bone. The prefrontal (Prf) forms the antero-superior part of the orbital rim; it is separated from the postfrontal by a slight supraorbital notch. Intero-laterally it is in clear sutural union with the frontal and the nasal; inferiorly it meets the lachrymal which it seems to overlap. At the superior anterior angle of the orbit there is a slight groove on the external aspect of the bone. Below this groove and 15 mm. above the suture with the lachrymal there is a very small projection towards the orbit below which is a slight concavity in the orbital rim. This may represent, in a negligible manner, the distinct emargination on which Lambe places great stress in his description of Gryposaurus notabilis. The frontal (F) meets its fellow in a slightly sinuous suture on the median line. Posteriorly it is bounded by the parietal to a point almost half way across the supratemporal fossa; here it meets the postfrontal, the suture with which runs forward to the supraorbital notch. The frontal, there- fore, is excluded from the orbital rim except at the very base of the notch. There is no indication of a small supraorbital in this notch as suspected by Lambe in the case of G. notabilis. From the notch to the fronto-nasal suture the frontal is bounded laterally by the prefrontal. The superior aspect is slightly concave. Head 13 The postfrontal (Pf) forms the superolateral margin of the head from the supraorbital notch to within a short distance of the posterior end of the upper temporal arcade. Internally it meets the parietal in a very irregular suture which passes downwards at about the middle of the anterior border of the supratemporal fossa. The suture with the frontal passes irregularly forwards and outwards to the supra- orbital notch. Nearly two-thirds of the postorbital bar is formed by a descending process of this bone which is much stouter than the ascending process from the jugal. There is a distinct concavity on the outer aspect of this process superiorly. The suture with the squamosal is uncertain but it seems to cross the arcade irregularly on the superior aspect and to run sharply forwards and downwards on the lateral aspect as in Gryposaurus notabilis. The parietal (Pa) meets its fellow in a very narrow and sharp crest between the supratemporal fossae. On the upper surface of the skull it is in sutural union only with the frontal ; laterally it joins the postfrontal, the suture passing irre- gularly downwards near the middle of the anterior border of the supratemporal fossa. Inferiorly the parietal is bounded by the orbitosphenoid anteriorly and by the prootic (?) posteriorly. The suture with the squamosal seems to be almost on the median line causing the parietals to terminate posteriorly in a narrow point. The sharp median crest of the united parietals which separates the two supratemporal fossae bifurcates anteriorly and each branch curves outwards around the intero-anterior angle of the fossa thus forming a clearly marked triangular area with concave sides at the junction of the parietals with the frontals. The squamosal (S) meets the postfrontal as described above and forms the whole of the posterior rim of the supra- temporal fossa. Posteriorly the bone descends abruptly into the nuchal depression where it seems to terminate against a small supraoccipital. From the outer side of the nuchal depression the posterior margin ranges upwards and forwards and then passes downwards to the extremity of the para- occipital process of which it forms the external and anterior 14 Kritosaurus incurvimanxjs faces. The suture with the exoccipital which forms the inner side of this process is very clearly marked by a distinct depression. Laterally there is a deep cotylus for the head of the quadrate in front of which a spur extends downwards a distance of 60 mm. from the rim above the cotylus. From the end of this spur to the suture with the postfrontal the inferior margin of the squamosal is deeply concave and forms the upper posterior rim of the postorbital fossa. Externally and above this rim the squamosal is concave and in the concavity lies a forwardly directed process which is in close contact with but apparently not united to the outer surface of the squamosal. The quadrate (Q) is a very long, shaft-like bone with an anterior wing for union with the pterygoid. It is slightly curved upwards and backwards and is excavated on the antero-lateral margin for union with the quadrato-jugal. The lower end is evenly rounded for articulation with the mandible. The quadrato-jugal (Qj) (Fig. 1) is a small, triangular bone terminating above in a thin acute angle: it is set into a distinct excavation on the antero-external side of the quadrate and is overlapped anteriorly by the jugal which is almost if not entirely out of contact with the quadrate. In this respect the present species more closely resembles Kritosaurus novajovitts thanGryposaurus notabilis. The external surface shows radiating lines of growth ; the anterior edge is very thin; the posterior edge is thicker; the interior posterior sur- face is hollowed where it fits into the depression in thequadrate. The jugal (J) is a long curved bone with a marked down- ward turn over the coronoid process of the mandible and with a slender ascending process which forms the lower part of the postorbital bar. It broadly overlaps the quadra to- FIG. 1 — Left quadrato-jugal. half natural size. One Head 15 jugal and almost touches the quadrate superiorly. Anteriorly the bone meets the lachrymal above and the maxilla below; it seems to have a marked outward inflection at the former suture, but this may be due to pressure. The maxillary (Mx) is a deep and massive bone strongly incurved superiorly, particularly in the posterior part: this incurving of the alveolar margin is so great that it lies 80 mm. internal to the outer face of the jugal. The usual prominent ridge runs backwards on the external face from the lower edge of the suture with the jugal. In front of this suture the bone greatly increases in height and is in sutural union with the lachrymal above. The relationship with the premaxillary is not shown. Close in front of the lower part of the suture with the jugal is a prominent, backwardly directed foramen ; 50 mm. in front of this and a little higher up is another (not shown in the plate). Nine maxillary teeth appear in a distance of 67 mm. Their structure is not well shown but they appear to be of the ordinary carinate type. The dentigerous groove is at least 55 mm. deep but its length can not be ascertained owing to the loss of the anterior part. Internally the maxillary is in contact with the pterygoid but the exact relationships are difficult to ascertain. The basioccipital (Boc) and exoccipital (Eco) are so fused that a sutural union can not be observed. That the latter bone contributes to the formation of the occipital condyle can not be stated, but that it bounds the foramen magnum laterally is almost certain. The occipital condyle is broad and slightly convex posteriorly on the horizontal line; vertically it is not very convex on the posterior aspect but turns sharply downwards and forwards at the postero-inferior angle. The under surface is broadly convex laterally; antero-posteriorly it is slightly convex in the rear and concave towards the front. The main articular surface looks strongly downwards. Viewed from the rear the condyle has a trifid appearance, as on either side, above and outwards from the main portion of the condyle, is a pronounced process with articular surface 1 6 Kritosaurus incurvimanus directed outwards and backwards. Above these structures the bone has a pillar-like appearance for a short distance. The inner surface of the pillar is continuous with the inner and upper surfaces of the articular tuberosities mentioned above and continues evenly inwards and forwards to form the lower half of the lateral boundary of the escutcheon- shaped foramen magnum. Above the pillar-like portion the bone may be resolved into two ascending, expanded elements which are continuous with each other. The inner of these rises from the pillar, passes forwards and upwards, and then strongly upwards and backwards terminating in a sharp ridge above which is a suture, in all probability with the supraoccipital. This section forms the upper half of the border of the foramen magnum, above and outward from which the bone is slightly but distinctly concave. The outer ascending section expands above the pillar-like part and turns outwards and downwards to form the postero- internal surface of the prominent paraoccipital process. Superiorly this part of the bone is greatly thickened and forms a prominence posterior to the squamosal from which it is separated on the superior aspect of the head by a conspicuous open suture. The relationship of the basioccipital to the bones of the temporal region is very doubtful as no actual sutures can be seen, and the surface of the bones is abraded in places. The coalesced occipital bones are in contact with the prootic above and possibly with a lateral ascending process from the basisphenoid below. Outwards from the anterior concave part of the under surface of the basioccipital is the usual well developed descending tubercle, the basioccipital tubercle (Boc. Tub.). On the lateral aspect of the bone above the tubercle is a small slit-like aperture, probably for the passage of an artery. Above and behind this is a sub-triangular foramen for a branch of the twelfth nerve. Behind this opening should be a foramen for the second branch but the condition of the bone prevents its recognition. Head 17 In front of the basioccipital tubercle there is a pro- nounced depression running upwards and backwards and terminating at a foramen for nerves IX to XI. No actual suture is to be seen in this depression but it is suggested that it may represent the line of union between the basioccipital and an ascending process of the basisphenoid. The supraoccipital is a small bone forming the floor of the pronounced nuchal notch; it is clearly separated from the thin ascending inner flange of the exoccipitals and it abuts laterally against the thickened upper part of the outer flange but no trace of a suture is to be observed. Anteriorly the bone is in contact with the squamosals and possibly touches the posterior thin edge of the united parietals in the midline. The sutures of the basisphenoid are all uncertain and the union ventrally with the basioccipital is entirely obscured. The bone doubtless forms the usual basal plate from which lateral processes seem to ascend between the orbitosphenoid and the basioccipital. Presumably this process is in union superiorly with the prootic but the only indication of such union is a slight crease which runs downwards and back- wards from the foramen of the fifth nerve. Latero-ventrally there is a stout rod-like process extending downwards and outwards to the pterygoid; this is the basipterygoid process of the basisphenoid (b.p.). Viewed from the rear this process maintains its rod-like appearance. In the midline postero- ventrally there is a median rod-like process extending down- wards and backwards to the pterygoids. The prootic shows a distinct suture above with the parietal and anteriorly with the upper part of the orbitosphenoid. The latter suture can be traced indistinctly to the large foramen of the fifth nerve below which it is lost. Posterior to this opening the bone has the appearance of a roughened bar between the foramina of nerve V and nerves IX-XI. The fenestra ovalis is a larger and the foramen of the seventh nerve a smaller opening in this bar. No epiotic or opisthotic can be distinguished and a union ventrally with the ascending process of the basisphenoid is conjectural only. 1 8 Kritosaurus incurvimanus The orbito sphenoid (O.sp) is a large and irregular element suturally united above with the parietal and postfrontal: it forms the inferior part of the anterior boundary of the supratemporal fossa and extends downwards in the rear of the orbit. A sharp plication of this downward extension forms the posterior border of the orbit in this region. There is a broad superior extension anteriorly which is in union with the prefrontal above and with the prespheno,id in front. The inferior sutures are all uncertain. In Plate III a suture with the parasphenoid is faintly indicated but this can not be regarded as at all certain. From the foramen of the fifth nerve downwards and forwards is a distinct parting with the upper portion overhanging the lower: this is possibly, but not certainly, a suture with the ascending process of the basisphenoid. The foramen of the fifth nerve is a large opening on the posterior border of the bone: it is continued forward as a distinct groove on the outer surface. The foramen of the fourth nerve enters the cranium from the rear of the orbit nearly on a level with the above groove. Immediately below, at the union with the parasphenoid, is a larger fora- men for the third nerve. The arrangement of the bones in the anterior part of the sphenoidal region seems to differ in several respects from that of other members of the family which have been figured. Extending forward from the foramen of the third nerve is a distinct vacuity which separates the parasphenoid from the orbitosphenoid and the presphenoid. Above this vacuity, on the intero-inferior margin of the forward extension of the orbitosphenoid, is a fairly large foramen, probably for the second nerve. Above this opening is a narrow longitudinal groove passing posteriorly into a small foramen, probably for a blood vessel. The parasphenoid (Pa.sp.) extends forward from the basipterygoid process of the basisphenoid ; its inferior margin is slightly concave as is also its outer face. Anteriorly the bone divides into a long inferior and a shorter superior process. Above, as already stated, it is separated by a. Head 19 distinct vacuity from the presphenoid and orbitosphenoid for the anterior three-fourths of its length. Posteriorly it seems to be in contact with the orbitosphenoid but the suture is practically obliterated. The presphenoid (Pre.sp.) is a small bone connected with the anterior wing of the orbitosphenoid by an overlapping suture; its antero-superior edge meets the frontal. The inferior margin is tongue-shaped and is separated from the parasphenoid by the vacuity already referred to. The pterygoid (Pt.) is a very irregularly shaped bone consisting essentially of four parts — a posterior horizontal expansion, a posterior vertical expansion, an anterior palatal portion connected with the maxillary, and a descending process. The horizontal posterior expansion is quite thin, meets its fellow in the midline, and its posterior free margin trends outwards and backwards to a suture with the quad- rate. Between the central and lateral inferior processes of the basisphenoid it arches upwards but it sinks into a depres- sion at the point of union with the lateral process (basi- pterygoid process). In front of the basipterygoid process the posterior vertical wing rises as a very thin sheet which extends backwards and outwards overlapping internally the forwardly directed wing of the quadrate. The anterior or palatal extension can not be differentiated as an ectopterygoid and it is so closely applied to the maxillary that a sutural line can not be clearly seen. This palatal portion is rounded superiorly at its posterior end; anteriorly it is inflected forwards, upwards, and in- wards, and meets, or almost meets, the corresponding bone of the other side. Inferiorly and in line with the posterior ascending process is a descending process which seems to overlap the posterior end of the maxillary, and with the lateral part of the horizontal plate to form a large concavity directed forwards at the upper angle of the posterior end of the maxillary. This part is badly broken and no sutures can be made out with certainty. 20 Kritosaurus incurvimanus The mandible is very robust and deep and is strongly inflected towards the alveolar border which is 80 mm. internal to the outer surface of the strong coronoid process. The preserved portion shows that the dentary was probably deflected anteriorly. Its suture with the angular follows the inferior margin of the mandible and can scarcely be seen in a lateral view. The suture of the dentary with the surangular sweeps downwards and backwards from the posterior margin of the coronoid to the inferior edge of the mandible. The suture of the surangular and angular follows the inferior margin to the posterior end. The articular turns in behind the foot of the quadrate; its sutures are not observable. The mandibular teeth (Plate IV) are not well exposed but they seem to be arranged in three or four vertical rows with the grinding surface highly inclined upwards and inwards. The total number of rows is, of course, indeterminable owing to the loss of the anterior part of the mandible; seven rows occur in a distance of 55 mm. A fragment of the mandible shows well preserved teeth but they are all split vertically except one of the innermost series which must serve as a type tooth for the species. This tooth is 18 mm. long and 5.5 mm. wide at midlength; it tapers downwards to a width of 2.5 mm. at the root. Up- wards from the point of maximum diameter the tooth con- tracts gradually to a fairly sharp point, the actual termination being slightly broken. The inner enamelled surface shows the usual carina which is quite low. Between the carina and the lateral margins, both above and below midlength, is a gently concave depression rising to an exsert edge. Above the middle, this raised edge carries eight small tubercles which are fairly evenly spaced except at the bottom where the lower two are more closely set. These tubercles look distinctly upwards. In shape the tooth resembles that figured by Brown for Kritosaurus novajovius; it is, however, much smaller and the papillae are larger, more clearly defined, and much less numerous. Moreover, the lateral margin is slightly raised Head 21 making the space between it and the carina concave and not flat as in Brown's species. With regard to the teeth of Gryposaurus notabilis Lambe says: "The teeth are of the usual trachodont type and are in from two to three rows in the grinding surface of the lower jaw. A satisfactory examination of the inner enamelled surface of the lower teeth has not been possible, but in two of the teeth seen from the inner side the margin appears to be smooth or nearly so." 1 In cross section the teeth show an exceedingly fine radial and concentric structure like that presented by a piece of fossil wood. Towards the roots the teeth seem to have been hollow ; they are embedded in a granular carbonaceous layer about 1.5 mm. in thickness. COMPARATIVE MEASUREMENTS OF THE HEAD Gryposaurus Kritosaurus notabilis incurvimanus Ft. In. Ft. In. Height of head from lower edge of dentary to highest point of squamosal. I 8 I 4! (415 mm.) Breadth between upper rim of orbits o.f 7 (178 mm.) Height of quadrate I 4J 1 l T V(345 mm.) Length of supratemporal fossa 6 55 (140 mm.) Width of supratemporal fossa 4 2 I ( 73 mm.) Height (oblique) of lateral temporal fossa 11 j 8yf (225 mm.) Width (horizontal) of lateral temporal fossa. ... 5I 45 (118 mm.) Height (oblique) of orbital opening 8| 6^(160 mm.) Width (horizontal) of orbital opening 5 ^(nomm.) Width of head at anterior of lachrymals 3yf-(ioomm.) Nasal — Width at suture with frontal 50 mm. Minimum width to prefrontal suture 40 mm. Depth (vertical) to the angle at the junction of premaxilla, lachrymal, and prefrontal 56 mm. Width of head across the two nasals, 120 mm. in front of orbit. . 60 mm. Lachrymal — Width 45 mm. Length 100 mm. Suture with prefrontal 45 mm. Suture with premaxilla 70 mm. 'Ottawa Naturalist, Vol. XXVII, No. 11, p. 148. 22 KritosauruS incurvimanus Prefrontal — Length 142 mm. Width on suture with lachrymal 45 mm. Width above orbit 38 mm. Frontal — Length on midline 70 mm. Width at supraorbital notch 80 mm. Postfrontal — - Length 175 mm. Bottom of descending process to top 113 mm. Horizontal width of upper temporal arcade 22 mm. Vertical width of upper temporal arcade 25 mm. Outer edge of upper arcade to interparietal suture 73 mm. Parietal — Length on median line of head 140 mm. Width at suture with frontal 35 mm. Width, interparietal to orbitosphenoid suture 55 mm. Squamosal — Width from suture with parietal to rim above cotylus for quadrate 118 mm. Posterior rim of supratemporal fossa to suture with exoccipital. . . 60 mm. Rim above cotylus to end of paraoccipital process 125 mm. Quadrate — • Length 345 mm. Diameter of shaft above quadrato-jugal 55 mm. Jugal — Total length 300 mm. Width below orbit 55 mm. Width below postorbital fossa 49 mm. Inferior edge to top of ascending process 150 mm. Basioccipital and exoccipital — Base of condyle (vertical) to supraoccipital suture 140 mm. Median line (horizontal) to end of paraoccipital process 130 mm. Median descending process of basisphenoid to posterior extremity of condyle (horizontal) 100 mm. Base of basioccipital tubercle to Nerve IX-XI 68 mm. Height of foramen magnum 50 mm. Width of foramen magnum 34 mm. Width across trlfid part of condyle 77 mm. Width of main part of condyle 65 mm. Supraoccipital — Length 37 mm. Width 72 mm. Orbitosphenoid — ■ Total length 115 mm. Height measured vertically 85 mm. Edge of orbital fold to posterior of foramen of fifth nerve 53 mm. Vertebral Column 23 Parasphenoid — Length from basipterygoid process to anterior end 125 mm. Pterygoid — Basal posterior sheet; midline to extreme point of suture with quadrate 125 mm. Basipterygoid process to anterior end of palatal portion 165 mm. Quadrato-jugal — Total length 130 mm. Total width 80 mm. Maximum width of part not overlapped by jugal 40 mm. Maximum thickness 14 mm. Mandible — Height of dentary, measured vertically from inferior to alveolar margin 102 mm. Extreme end of articular to front edge of coronoid process 218 mm. VERTEBRAL COLUMN The vertebral column is divisible into a cervical region of thirteen vertebrae, a dorsal of sixteen, a sacral of nine, and a caudal of undetermined number of which seventeen are preserved. The atlas (Fig. 2) consists of four pieces — hypocentrum, odontoid, and two halves of the neural arch. The hypo- centrum (intercentrum) is a rather stout, transversely curved, ventral bone about 90 mm. wide. The anterior ventral edge is rather sharp but the upper edge is excavated for the odontoid. The thickness (ant-post.) is about 30 mm. The posterior face fits, in a sinuous manner, into a trans- verse ventral groove on the anterior face of the axis; this groove is deeper towards its upper centre. The odontoid fits into the curved upper margin of the hypocentrum ; it measures 65 mm. transversely and rather less vertically. The anterior face shows a rounded ventral margin but the bone is FIG. 2 — Atlas and axis, right lateral view. One fourth natural size, a, centrum of axis; b, parapophysis of axis', c, diapophysis of axis; d. neural spine of axis; h, hypocentrum of atlas; o, odontoid; n, neural arch of atlas. 24 Kritosaurus incurvimanus distinctly concave supero-anteriorly. The posterior face is not well shown but it seems to be slightly convex and to abut against a forwardly directed convexity situated on the anterior face of the axis above the groove for the hypocentrum. The neural arches surround the superior part of the odontoid and almost touch the hypocentrum. Each arch measures 92 mm. vertically. The main basal part is 40 mm. long and 20 mm. thick near the lateral line of the column; it slopes forward to a rather sharp edge and upwards to the maximum height of the spine which is well forward. The superior edge slopes down, back, and slightly outwards, 71 mm., to a pronounced point, the postzygopophysis, which overlaps the stout prezygopophysis of the axis. From this point the posterior margin is slightly concave and extends outwards 40 mm. forming a stout diapophysis 30 mm. long antero-posteriorly. The two halves of the arch touch at the summit but diverge posteriorly; it is impossible to say whether or not there is a real union at the point of contact. The centrum of the axis (Fig. 2) is 70 mm. long on the lateral line and 78 mm. long on the ventral line: it is strongly opisthocoelous but the anterior face is relatively flat with a transverse inferior groove for the hypocentrum of the atlas; this groove is deepest in the centre but above the depression the face of the centrum extends forward in a convexity which seems to be in contact with the odontoid. Rather low, and well forward on the lateral aspect of the centrum, is a large blunt process or parapophysis. The neural arch is very large and extends into a plate- like spine 125 mm. long postero-anteriorly reaching forward between the arches of the atlas almost to the summit of the spine. A slender diapophysis occurs in the usual position; from its base a strong ridge runs backwards and upwards on the plate-like spine and terminates in a pronounced point in the supero-latero-posterior position. This point is 50 mm. from the posterior end of the spine proper. Thirty-eight millimetres below the point is a well developed postzygo- Vertebral Column 25 FIG. 3 — Sixth, seventh, and eighth cervical vertebrae, viewed from below and slightly from the right; left side not shown. One fourth natural size. d, diapophysis; pz, postzygopophysis; c.r., cervical rib] f, foramen. pophysial facette which strongly overlaps the prezygopo- physis of the third vertebra. The total height of centrum and spine is 160 mm. The remaining cervical vertebrae (Figs. 3 and 4) do not differ from one another except in a gradually increas- ing size posteriorly. The third vertebra is at least 85 mm. long; it is strongly opisthocoelous and correspondingly convex anteriorly, indicating much latitude of movement. There is a lateral foramen in the centrum. The parapophysis is smaller and higher up than that of the axis. The pre- zygopophysis is stout and outwardly directed; the post- zygopophysis is very robust and is the most conspicuous part of the arch; it is directed outwards, upwards, and back- wards to a length of 80 mm. and carries a wide articular facette. The neural spine is very small, not over 18 mm. high. The remaining cervical vertebrae resemble the third except for some details of measure- ment. The centra gradually increase in length from 85 mm. in the third to 100 mm. in the thirteenth. The diapophyses in- crease from 40 mm. in the third tO 140 FIG. 4 — Sixth, seventh, and eighth cervical vertebrae, viewed . from the right. One fourth natural size. mm. in tile tnir- us ^ neural spine; pz, postzygopophysis; d, diapophysis] c.r., , , 1 cervical rib ; p, capitular branch of rib fused with parapophysis: teenth, measured s, foramen. 26 Kritosaurus INCURVIMANUS in a slightly oblique direction from the hollow in the centrum between the parapophysis and the diapophysis. The neural spines are pointed and directed strongly backwards; they increase in length from 18 mm. in the third to 50 mm. in the thirteenth vertebra. The postzygopophyses increase fro|m 80 mm. in the third to 120 mm. in the ninth vertebra and then gradually decrease to a length of only 75 mm. in the thirteenth vertebra. The measurement is from the lower posterior angle of the neural spine to the extremity of the process. In the posterior cervical region, where the curvature of the neck is greatest, the postzygopophyses are pushed down so far that they appear on the ventral side with the articular facettes quite exposed. The thirteenth cervical bears a much larger rib than the twelfth and on this account might be considered as a dorsal. On the other hand, the fourteenth vertebra bears a strong postzygopophysis like those of the cervicals, whereas that of the fifteenth is conspicuously different. The distinctly dorsal rib of the fourteenth prohibits the possibility of including it among the cervicals; therefore, the possession of a very large postzygopophysis can not be made the basis of division. The dorsal vertebrae are sixteen in number. Owing to a parting along the base of the neural spines in removing the skeleton from the quarry, and to the necessity of leaving the matrix for the support of the ribs and muscles the char- acteristics of these vertebrae are only partly revealed. The centra increase in width and height but decrease in length; the sixteenth is 68 mm. long and appears to be amphiplatyan. The total height of this vertebra, from the base of the centrum to the top of the spine, is 438 mm. The neural spine of the first dorsal is considerably larger than that of the last cervical. From a length of 90 mm. in the first the spines increase in length to 135 mm. in the second, 160 mm. in the third, 210 mm. in the eighth, and 230 mm. in the sixteenth vertebra. The first four spines, like those of the posterior cervicals, are pointed and directed backwards ; the fifth and sixth are less pointed but still with Vertebral Column 27 a backward inclination; the seventh is more erect, broader, and with a square top. The remaining dorsal spines are similar to the seventh and have an average width of about 80 mm. The diapophyses of the dorsal vertebrae are very stout processes directed outwards and slightly upwards and with a strong backward inclination in accord with the direction of the neural spines. The first and second are relatively slender, quadrangular in cross section, and about 150 mm. long measured from the base of the neural spine. As the centra are covered these processes can not be measured in the same manner as those of the cervicals. The thickness (ant- post.) is about 30 mm. The third diapophysis has the anterior edge drawn out to a sharp flange near the point of origin and this feature becomes more pronounced in the succeeding vertebrae. Similarly the posterior edge of the process gradually assumes a like character, the flange merging into a backwardly directed extension at the base of the neural spine. These extensions function as pre- and postzygopo- physes respectively, the former overlapping the latter. The diapophyses decrease in length from 150 mm. in the first to 1 10 mm. in the last dorsal vertebra. The sacrum is composed of nine fused vertebrae followed by a tenth which presents some features common to the other sacrals. Its transverse process is remarkably like that of the ninth sacral and sharply different from that of the first of the caudal series; I propose to regard this vertebra as a sacro-caudal and to include it in the caudal region. The first sacral centrum is firmly fused to the second and is much longer than the last dorsal, but it seems to bear no transverse process. On this account some authors would regard it as a dorso-sacral. The first four sacral centra are about 80 mm. long; the fifth, sixth, and seventh are not observable; the last two are somewhat shorter being about 70 mm. in length. The diapophyses of the sacral vertebrae, viewed from the dorsal aspect, seem slighter than those of the posterior dorsals; the anterior ones are directed forwards but the 28 Kritosaurus incurvimanus last two are bent backwards, perhaps by pressure. Near the point of origin the anterior edge is inclined downwards and the posterior edge upwards resulting in ill defined pre- and postzygopophyses the former of which seem to overlap the latter. The postzygopophysis of the first vertebra is more pronounced than those of the succeeding sacrals, but the arrangement of the articular surfaces, if such exist, is not well shown. The first three diapophyses are close together (30-40 mm. interval) ; the fourth to seventh are about 70 mm. apart; the eighth and ninth are bent backward and crowded together. The extremities of the first four diapophyses are hidden under the anterior ramus of the ilium which extends 250 mm. in advance of the first. The fifth to ninth come in contact with the superior margin of the posterior ramus of the ilium. The height of the seventh diapophysis, measured from the base of the neural spine, is 160 mm. The firsf four neural spines of the sacrum are curved strongly backwards as they spring from the arch but assume a direction nearly at right angles to the column at their extremities. The blade is broader than those of the neigh- bouring dorsals, averaging about 90 mm. The length along the median line is about 280 mm. The posterior edge of the curved part of each of these spines is inclined outwards and is continuous with the similarly inclined posterior edge of the diapophysis; this results in an overlapping proximally of the posterior by the anterior spine. The remaining neural spines of the sacral region are less curved, do not overlap distinctly, and are narrower in the blade, not exceeding 80 mm. as in the case of the posterior dorsals. Provisionally the structures arising from the sacral centra for the support of the pelvis will be called parapophyses (vide posted). As- already stated the first sacral bears no such structure; that of the second rises as a broad plate at the extreme anterior edge of the centrum where it is continuous with the lateral face of the first centrum. This process extends back, out, and down, narrowing towards the centre and expanding distally; it seems to be quite separate from he diapophysis, but this can not be stated with certainty. Vertebral Column 29 The corresponding structure of the third sacral is quite different as it assumes the form of a vertical plate at the anterior edge of the centrum, and is, apparently, in contact with the diapophysis throughout its length. These two parapophyses unite ventro-laterally and seem to be attached to the acetabular border of the pubis. The corresponding structures of the fourth, fifth, and sixth sacral vertebrae can not be seen but they are probably similar to that of the third. The seventh vertebra bears a stout transverse plate, anteriorly placed, strongly inclined forwards, continuous with the anterior edge of the diapo- physis, and attached to the postacetabular border of the ilium; it is about 90 mm. long. The parapophysis of the eighth sacral vertebra rises at the extreme anterior edge of the centrum as a vertical plate directed straight outwards. Its general position is slightly anterior to the diapophysis with which it is connected throughout its length; it expands distally and is attached to the upper inner side of the posterior ramus of the ilium, whereas the extremity of the diapophysis appears over the superior margin of that bone. The ninth sacral vertebra has no distinct parapophysis but the diapophysis is stouter and more expanded than that of the succeeding sacro-caudal vertebra. Its anterior edge is drawn out ventrally and extends some distance down on the centrum, thus taking the place of the more distinct para- pophyses of the anterior sacral vertebrae. Whether these so-called parapophyses are to be con- sidered as separate ossifications, and, therefore, as sacral ribs, is open to question, as the nature of the union with the diapophyses is in no case clearly revealed. The first para- pophysis, that of the second sacral vertebra, is disconnected from the diapophysis and shows no sign of sutural union with the centrum with which it appears to be quite con- tinuous. On the other hand, the corresponding structure of the sixth vertebra seems to have a very distinct sutural union with the centrum. Seventeen caudal vertebrae are preserved (Fig. 5). The centra gradually decrease in length from 70 mm. to 55 mm. 30 Kritosaurus incurvimanus and in height, measured from the ventral side of the base of the transverse process to the ventral anterior edge, from 105 mm. to 80 mm. The total height of the centra is not observable for the whole series, but the fifth is 130 mm. and the seventh about 85 mm. As the left side is buried in the matrix the width of the centra can not be measured; the tenth is estimated to be 1 10 mm. wide. The transverse process of the pj first caudal vertebra, regarded as a sacro-caudal, is a stout structure 100 mm. long; it is arched dorsally, i.e., it at first ascends and then descends. The distal end is expanded and is 60 mm. wide antero-posteriorly; it touches the extreme posterior end of the ilium and almost touches the transverse process of the last sacral. On account of the resemblance of this process to that of the preceding vertebra and of its sharp differentia- tion from that of the next succeeding, the vertebra is regarded as a sacro- caudal. The transverse processes of the remaining caudals are slender, curved, somewhat variable, spine-like structures flattened dorso-ventrally. They arise from the superior lateral angle of the centra, in the proximal vertebrae rather far forward, but in the distal vertebrae more towards the posterior. From a length of 90 mm. on the second caudal, these processes decrease gradually in length to a mere spur of five millimetres on the seven- teenth. The neural spines of the caudal vertebrae curve back- wards with the concavity of the curve anterior. The length decreases from 300 mm. in the third to 230 mm. in the twelfth which is the last that can be measured with certaintv. The FIG. 5 — Eleventh and twelfth cau- dal vertebrae. One eighth natural ?ize. n.s., neural spine] Poz, postzygopo- physis; d. transverse process] Pz. prezygopophysis; c. chevron. Shoulder Girdle 31 blade decreases in width from 60 mm. in the first to 50 mm. in the tenth. A small postzygopophysis with an articular facette is overlapped by a somewhat stronger prezygopophysis ; this is the opposite of the condition observed in the cervical and dorsal regions. The chevrons are long and slender and seem to have two articular facettes on the slightly expanded head. In the region immediately below the head the diameter is somewhat reduced by the incurving of the posterior margin. The maximum width observed in the largest chevron is about 25 mm. The first chevron, which occurs between the fifth and sixth caudal vertebrae, is 250 mm. long; the second and longest chevron measures 310 mm. The length gradually decreases to 256 mm. in the eleventh. Shoulder Girdle and Fore Limb Except for some peculiarities in the structure of the coracoid and the manus, the bones of the fore limb are essentially the same as in other members of the group. The radius and ulna are shorter than the humerus as in Claosaurus and Hadrosaurus. Compared with Claosaurus annectens, an animal of equal size, the long bones of the fore limb are one-fourth greater, whereas the scapula is con- siderably shorter. The scapula (Figs. 6 and 7) is a large bone with a broad, blade-like upper end and a greatly expanded and massive lower or articular end. The blade terminates above in a remarkably straight line and is not rounded as in most members of the group. The figure given in the preliminary description is incorrect in this respect; it was prepared from the imperfect left scapula and is herein corrected by the almost perfect outline of the right or under bone. The maximum width of the blade is not more than an inch below the extreme end. From this point downwards the blade gradually narrows and thickens reaching its minimum width about 300 mm. from the articular end. Kritosaurus ixcurvimanus The outer face of the bone is very flat in the upper third, but downwards it becomes more convex. The crest of the convexity ranges forward and becomes a decided prominence on the antero- external face of the lower part of the bone, treme About lower mm. from the ex- this crest falls off rapidly but rises again to a less extent over the articular surface for the coracoid. The margin of the crest where it be- gins to descend is deflected forward and has the appear- ance of an articular surface. It has been suggested that this surface- was possibly in contact with a clavicle; on this account it will be called the clavicu- lar crest. Between this crest and the pos- tero-inferior mar- gin of the bone 0— Left scapula, externa! where it Swells OUt to form the glenoid cavity is a deep depression. The end of the clavicular crest and the swollen margin above the glenoid cavity are almost on a line at right angles to cor' FIG view. One eighth natural size, g.c., glenoid cavity; cor, articular surface for cor- acoid. FIG. 7 — Left scapula; in- ternal, proximal, and dis- tal views. One eighth natural size, go, glenoid cavity, cor, articular surface for cor- acoid. Shoulder Girdle 33 the axis of the bone. This line is 90 to 100 mm. above the extreme end of the bone. The interior face of the scapula is very fiat to the point of minimum diameter below which is slopes up very gradually to the edges of the articular facettes. The posterior edge of the bone is concave, thin, and sharp to within 80 or 90 mm. of the glenoid cavity where it rapidly expands. The anterior edge is convex and less sharp. Proximally it merges into the side of the clavicular crest which is slightly hollow anteriorly. The extreme lower anterior border ranges forward to form the edge of the facette for the coracoid. The proximal view shows two distinct articular cavities; the anterior or coracoidal cavity is the larger and looks slightly inwards; the posterior or glenoid cavity is 90 to 100 mm. distal to the anterior and looks almost straight downward. The coracoid (Fig. 8) is a small but fairly heavy bone, quite separate from the scapula with which it was in free articular union as shown by the smooth surfaces of the facettes of both bones. The coracoid may be resolved into two portions — an ex- panded proximal artic- ular region, and a distal or anterior flange-like vertical extension. The proximal expanded portion bears a wide convex articular facette for the scapula and a concave facette for the humerus. The two facettes are separated by a deep foraminal notch as in Iguanodon and Camptosaurus. As the animal has every appearance of being adult it is doubtful if this notch ever became closed as in most tracho- FIG. 8 — Left coracoid; external view; glenoid cavity; f.n.. foraminal nolch\ s.c, scapular articulation. 34 Kritosaurus incurvimanus donts. The scapular facette looks rather more inward than that for the humerus. The vertical expanded portion in front of the scapular facette decreases in diameter, at first gradually, and then more rapidly to a blunt rounded edge. In front of the glenoid facette the decrease in diameter is more rapid at first and then very gradual to an anterior edge which is thinner and longer than that in front of the scapular facette. These two parts of the anterior edge are not in line with each other, but the upper overlaps the lower externally thus giving the bone a twisted appearance when viewed from in front. The lower anterior edge shows a broad sweeping convex curve downwards to a prominent point, from which the inferior margin rises in a concave curve to the edge of the glenoid facette. The inner face of the bone, in front of the scapular facette, is comparatively flat and slopes gradually forward to the upper anterior edge. Owing to the twisting already referred to, the upper end of the lower anterior edge forms a prominent point on the internal aspect of the bone. The figure of the left coracoid which accompanies the preliminary description shows an emargination of the lower anterior edge; this must be due to injury as the better preserved right bone shows no such indentation. The major limb bones of trachodont dinosaurs are so much alike that an opportunity for detailed comparison is necessary for an adequate description. The table of measure- ments at the end of this section is of more value than a detailed accoulnt of the bones. The humerus (Fig. 9) was badly injured, particularly in the region of the radial crest, but its general characteristics as determined from both bones are fairly well revealed. The figure given by Lambe for the humerus of Stephanosaurus marginatus might serve to illustrate the present species except for some details of measurement. 1 The humerus is a heavy bone, shaft-like in its lower third. Di stally this shaft expands both laterally and antero- 'Contributions to Canadian Palaeontology, Vol. Ill, Geol. Sur. Can. Fore Limb 35 posteriorly into the inner and outer condyles, which are separated on both the anterior and posterior sides by distinct concavities. Both condylar expansions are conspicuously flattened externally; the planes of flattening are not parallel but inclined towards each other pos- teriorly. The articular surface of the inner con- dyle is sub-rhomboidal in outline and that of the outer sub-triangular. Above the constricted shaft the bone expands in two directions; antero- extemally into the very prominent radial crest which continues upwards into the outer tuberosity, and posteriorly into a ridge, obliquely trans- verse to the above, which continues upwards into the inner tuberosity. On the anterior face these two expansions are separ- ated by a slightly concave area and on the posterior face by an intermediate convexity which rapidly expands into the promin- ent head. A proximal view shows the outer tuberosity as the lightest element, inclined slightly backwards and separated by a slight concavity from the head, which is robust and posteriorly situated. The inner tuberosity is intermediate in size be- tween the head and the outer tuberosity and is not separated from the head by a marked depression. FIG. 9 — Left humerus; A, inner front view; B, outer rear view. One eighth natural size. h, head; oc. outer condyle; ic, inner condyle; r, radial crest; it, inner tuberosity; ot, outer tuberosity. 36 KklTOSAURUS INCURVIMANUS VS m I Ml The humerus in this species is longer than in Trachodon mirabilis, Claosaurus annectens, Saurolophus, or Hypacro- saurus; it is shorter than that of Lambe's Stephanosaurus marginatas. The radius and ulna (Figs. 10, n, and 12) show no striking features to distinguish them from the similar bones of other trachodonts. The relative length of these bones with respect to that of the humerus is regarded as a feature of generic value. In Kritosaurus, the ulna, over the olecranon process, is slightly shorter than the humerus and the radius is considerably shorter. This relation- ship is observed in Trachodon and Hadrosaurus, while in Saurolophus the bones are of equal length, and in Hypacrosaurus the radius is much the longer bone. The bones of the two sides agree closely in detail of measurement but there is con- siderable difference in the amount of curva- ture. The figures are based on the straighter bones of the left side but the more perfect radius of the right side has been used for some of the detail. The ulna is a shaft-like bone with its minimum girth about 100 mm. above the lower end; the cross section at this point is sub-triangular and this outline becomes more pronounced as the bone expands distally to the articular surface. Above the minimum girth the bone expands in three directions; postero-internally into a thin and prominent flange, anteriorly into a less pronounced flange, and externally into a heavy ridge, or continuation of the shaft, which terminates above the proximal articular surface in the prominent olecranon process. The top of the radius fits nicely into the pronounced con- cavity between the first and second of these expansions. The proximal articular surface FIG. 10 — Left radius and ulna, anterior view. One eighth natural size. u, ulna ; r. radius ; o, olecranon pro- cess; c\ larger car- pal] c", smaller carpal. Fore Limb 37 is L-shaped, with the olecranon at the angle of the L. The distal articular surface is almost flat and triangular in outline. The flat- tened side of the bone is closely applied to a similar flat side of the radius. On the posterior side, above the distal end, there is a slight concavity extending some distance up the bone. The radius is a simple, shaft- like bone, gently expanding to- wards the distal end and more abruptly towards the proximal end. The articular surface for the humerus is flat and ovoid in outline, while that of the distal end is sub-triangular and more rounded. Two car pals were found in each limb. The larger is a sub- triangular bone with a greatest edge of about 40 mm. In the left foot it lies in the anterior position between the ulna and radius and is more closely asso- ciated with the latter which is rounded near its distal contact with the ulna to receive the carpal. In the right foot the bone is shifted to a posterior position. The smaller carpal is a bone of doubtful shape, apparently irregu- larly discoidal to flattened ovoid. In both instances it was found, a short distance above the articular surface, in the hollow on the posterior face of the ulna. While the carpal could scarcely have occupied this position in life, the I f.iir 38 Kritosaurus IXCURVIMAN'US FIG. 12 — Left radius and ulna, proximal view. One fourth natural size. similarity of position in the two legs seems to indicate that in each instance it was pushed a little upwards and that it actually occurred in the posterior position at the distal end of the ulna. The left bone is 28 mm. and the right only 12 mm. in diameter. All four carpal bones are imperfectly ossified as shown by the failure of distinct surfaces. Both front feet were found with the palmar surface upwards. Of the left foot every bone was intact and practically in place; of the right foot the ungual of the second digit was about twelve inches out of position and the second phalanx of the same toe was not recovered. In both feet the second metacarpal, together with its phalanges, was drawn slightly upwards and its proximal end inflected inwards on the palmar side. In both cases, also, the fifth digit was flexed towards the palmar surface. The man us of Trachodon has been the subject of some discussion. Brown, in 1912, reviewed the evidence and gave the following phalangeal formula: Digit II with three phalanges, the third a hoof. Digit III with three phalanges, the third a hoof. Digit IV with three phalanges, no hoof. Digit V with three phalanges, no hoof. 1 In 1 913 Lambe described the manus of a trachodont from the Edmonton formation in which the phalangeal formula was quite different from that given by Brown for the family: Digit II with three phalanges, terminal presumably a hoof. Digit III with three phalanges, terminal a hoof. Digit IV with two phalanges, terminal a hoof. Digit V with two phalanges, terminal a hoof.- 'The Osteology of the Manus in the family Trachodontidae, Barnum Brown, Bull. Am. Mus. Nat. Hist., Vol. XXXI, Art. 10. -The Manus in a specimen of Trachodon from the Edmonton formation of Alberta, Lawrence M. Lambe, Ottawa Naturalist, Vol. XXVII, Xo. 2. Fore Limb 39 The manus of Kritosaurus (Plate V and Fig. 13) differs from both the above and shows the following phalangeal formula: Digit II with three phalanges, the third a pointed hoof. Digit III with three phalanges, the third a blunt hoof. Digit IV with three phalanges, no hoof. Digit V with four phalanges, the terminal a small ovoid bone. The manus of Kritosaurus is comparatively small. The relative lengths of the different elements of the fore limb show the closest resemblance to the proportions of Claosaurus annectens. The humerus is 1.25 the length of that of C. annectens, and the radius is 1.26. The average of the third and fourth metacarpals, however, is only 1.04 that of C. annectens. Metacarpal II is a fairly straight bone, slightly swollen in the middle and but little expanded at the articular ends. The external side is flattened, particularly at the distal end, and is closely applied to the internal side of metacarpal III, but the relationship is not so intimate as between metacarpals III and IV. 1 Metacarpal III is a con- siderably longer and heavier bone with a slight twist, and is but little expanded towards the ends. The external side is flattened, particularly towards the ends, and is closely applied to metacarpal IV. Proximally this flattening causes the outer anterior angle to appear as a 'In all descriptions of the limb bones the terms internal and external are used with reference to the axis of the body, not of the limb. FIG. 13— Left manus. size. One fourth natural 40 Kritosaurus incurvimanus sharp ridge. Internally, towards the palmar side, the bone is similarly flattened to fit against metacarpal II. Both proximally and distally the posterior side is elevated into a triangular keel. Both articular surfaces are slightly convex; the proximal is sub-triangular and the distal sub-quad- rangular. Metacarpal IV is of about the same length as metacarpal III and is flattened on its inner side for close connection with that bone. The proximal expansion is greater than in metacarpal III; the distal expansion is much lighter than the proximal and almost at right angles to it giving the bone a decided twist. Both articular surfaces are slightly convex. Metacarpal V is a much smaller bone, divergent, and with no apparent connection with its neighbour. The proximal end is greatly expanded with an elliptical, concave articular surface. The distal end is smaller with an oblique and convex articular surface. The phalanges of the first row (Plate V) are comparatively long bones; thpse of digits II, III, and IV are flat to slightly concave proximally; that of digit V is convex. The distal ends are expanded, with articular surfaces of much greater extent than those of the bones apposed to them. The bones of the second row of phalanges are very much smaller, that of digit V being much the longest. Phalanges II 2 and III 2 are small and distinctly triangular and must have caused an inward inflection of the hoofs: this has suggested the rather ill-formed specific name of incurvimanus. One tri- angular bone of this kind, similarly placed in digit II, is described by Lam be {op. cit.). Brown states that this phalanx in digits III and IV is slightly triangular. His figure shows that the bone in digit III is but slightly tri- angular with the edge inwards as in Kritosaurus. The triangular aspect is more pronounced in the case of digit IV but the thin edge is here on the outside. In both these cases the proximal articular face of the bone is as large as the apposed surface of the first phalanx; in Kritosaurus the bone is much reduced reaching only part way across the distal end of the first phalanx. The evidence seems to suggest Fore Limb 41 that the family was in process of acquiring rather than of losing hoofs. Phalanx IV 2 is a normal bone, but very short and with a remarkably small articular surface proximally. Had not this bone been found in place in both feet one would think that a phalanx were missing. The third row of phalanges differs in each digit: II 3 is a somewhat inequilateral and pointed hoof; IIP is a broader, inequilateral, shorter hoof; IV 3 is a small flattened bone with a distal surface strongly suggestive of still another phalanx or a nail; V 3 is very like V 2 except for its smaller size. A fourth phalanx appears only in the fifth digit; it is a very small sub-spherical to ovoid bone. In the following tables of comparative measurements the species referred to are designated by Roman numerals as follows : Kritosaurus incurvimanus I Trachodon mirabilis II Claosaurus annectens Ill Saurolophus osborni IV Corythosaurus casuarius V Stephanosaurus marginatus (Lambe's original figures) VI Hypacrosaurus altispinus VII In the case of Kritosaurus the figures given are the averages of the measurements of the bones of both sides. COMPARATIVE MEASUREMENTS OF SHOULDER GIRDLE AND FORE LIMBS I II HI IV V VI VII mm. mm. mm. mm. mm. mm. mm. Scapula — Length 776 900 810 970 890 Maximum width of blade 189 220 200 230 200 Minimum width of blade 120 Maximum width at articular end. . 214 Thickness from clavicular crest to inner face 103 Length of scapular portion of glenoid cavity no Width of same 64 Facette for coracoid, length 80 Facette for coracoid, width 60 42 Kritosaurus incurvimanus Comparative Measure ments of Shoulder Girdle and Fore Limbs — Cont. I II HI IV V VI VII mm. mm. mm. mm. mm. mm. mm. Scapula — Height of clavicular crest from outer face of bone 67 Coracoid — Anteroinferior point to upper edge of scapular facette 200 215 Anteroinferior point to lower edge of glenoid facette 73 Width of scapular facette parallel to foraminal notch 80 Height of scapular facette at right angles to notch 65 Depth of notch from inferior edge of scapular facette 35 Width of glenoid facette parallel to notch 95 Height of glenoid facette at right angles to notch 78 Thickness of lower anterior expan- sion 22 Thickness of upper anterior expan- sions 38 Thickness in front of notch 52 Humerus — Total length 630 610 501 500 683 580 Breadth at lower end of radial crest 170 165 Circumference of shaft 214 255 265 Breadth across head and outer tuberosity 138 140 Breadth across head and inner tuberosity 130 130 Breadth across inner and outer tuberosities 160 145 Breadth of inner condyle (ant. post.) 82 80 Breadth of outer condyle (ant. post.) 80 100 Transverse width of inner condyle. 50 100 no 85 Transverse width of outer condyle. 52 Thickness of bone between the con- dyles 28 Thickness of head 78 Fore Limb 43 Comparative Measurements of Shoulder Girdle and Fore Limbs — Cont. I II HI IV V VI vn mm. mm. mm. mm. mm. mm. mm. Humerus. Thickness of inner tuberosity 41 Thickness of outer tuberosity 31 Vina — Length over olecranon process ... . 610 680 500 630 708 750 Length between articular ends .... 574 Circumference of shaft 158 190 170 Greatest width across coronoid process 104 145 Greatest width of antero-posterior expansion 75 94 Greatest diameter of distal end. ... 79 74 Least diameter of distal end 53 57 Radius — Total length 555 620 440 600 632 700 Circumference at middle 136 175 120 155 Thickness of proximal end, obliquely in and back 83 86 Thickness of proximal end, ob- liquely in and forward 64 54 Thickness of distal end, obliquely in and back 70 87 Thickness of distal end, obliquely in and forwards 50 50 Manus — Matacarpal II, length 185 250 200 245 220 " " maximum diameter proximal end — 39 " " maximum diameter distal end 37 Metacarpal III, length...' 226 330 220 265 " " maximum diameter proximal end 49 " " maximum diameter distal end 50 Metacarpal IV, length 225 330 215 280 " " maximum diameter proximal end 68 " " maximum diameter dis- tal end * 51 44 Kritosaurus incurvimanus Comparative Measurements of Shoulder Girdle and Fore Limbs — Cont. I II HI IV V VI VII mm. mm. mm. mm. mm. mm. mm. Metacarpal V, length 94 130 75 120 " " maximum diameter proximal end 52 " " maximum diameter dis- tal end 35 Phalanx II 1 , length 75 " proximal width 45 " " distal width 42 Phalanx IP, length 18 " " width 25 Phalanx IP, length 64 " proximal diameter 37 " width of hoof 53 Phalanx IIP, length 57 " proximal diameter 51 " " distal diameter 47 Phalanx IIP, length 21 " " width 34 Phalanx IIP, length 52 " " proximal width 45 " " width of hoof 58 Phalanx IV 1 , length 66 " proximal diameter. .' 52 " " distal diameter 53 Phalanx IV 2 , length 18 " width 34 Phalanx IV s , length 15 " width 21 Phalanx V 1 , length 60 Phalanx V 2 , length 32 Phalanx V 3 , length 18 Phalanx V 4 , length 10 Ribs and Sternal Bones Cervical ribs (Figs. 3 and 4) are borne by all the vertebrae of the neck except the atlas; they are of the usual double- headed type with the tuberculum fused to the postero- ventral side of the diapophysis at its extremity, and with the capitulum similarly and more completely fused to the parapophysis. Ribs 45 The rib of the axis, really the first but herein called the second to accord with the number of the vertebra, is different from those immediately posterior to it. As the bone was broken and displaced the following description can not be relied on absolutely. The posterior branch is relatively long, narrow, and very thin; it measures 100 mm. from its ex- tremity to the tuberculum. The capitular branch is broad, flat, and extremely thin; apparently, it was attached to the relatively large and low-set parapophysis ; by lateral expan- sion it merges with the posterior and tubercular branches; it measures 70 mm. from the capitulum to the tuberculum. This rib differs from the others in its greater length, more delicate structure, and in the fact that the three branches lie almost in one plane. The remaining cervicals conform to a uniform structure but they show considerable variation. Of the anterior branches, the capitular is always the more important and increases gradually in length distally. The tubercular branch is slightly concave in its anterior margin and shows a fairly sharp point at the union with the capitular branch; this point is continued backwards as a gradually diminishing ridge on the face of the posterior branch. The second to fifth cervicals are very much alike and have a slender and rather pointed posterior branch which measures about 85 mm. from its extremity to the tuberculum. The sixth to tenth cervicals differ from the anterior ones in that the posterior branch is flattened dorso-ventrally instead of being evenly pointed. Measured fro,m the tip of the posterior branch to the tuberculum this set of cervicals shows the following lengths: sixth, 70 mm. ; seventh, 63 mm. ; eighth, 54 mm. ; ninth, 58 mm. ; tenth, 68 mm. While there is no increase in length these ribs become gradually more robust distally. The capitular branch, measured in a straight line from the centrum immediately behind the parapophysis, increases gradually from 40 mm. in the sixth to 63 mm. in the tenth. The eleventh and twelfth cervicals have pointed posterior branches resembling those of the more anterior ribs ; measured 46 Kritosaurus incurvimanus from the tuberculum these branches are respectively 80 mm. and 120 mm. in length. The capitular branches are pos- teriorly directed; measured as in the case of the previous set, they show lengths of 80 mm. and 97 mm. respectively. The thirteenth cervical rib is a very much stouter bone resembling the first dorsal more than the twelfth cervical. It is at least 240 mm. long but its extremity is hidden under the scapula and can not be seen. This rib is considered as belonging to the cervical series because the capitular branch is well out of contact with the diapophysis, and because the postzygopophysis of its vertebra is distinctly cervical and not dorsal in character. There is little doubt, also, that both capitulum and tuberculum are firmly fused with their supports. Dorsal ribs are borne by all the vertebrae of the series except the last. The tubercular branch is very short with a rounded termination; the capitular branch is very stout and is in fairly close contact with the an tero- ventral side of the diapophysis. In no case can the manner of its attach- ment to the parapophysis be seen, but with the greater ribs, it must have a length of at least 160 mm. The ribs are thicker and with a rather square edge on their anterior sides, whereas the posterior edge is thinner and more acute. The third to fifth ribs are the stoutest, with a maximum width of 38 mm. The length of each rib is indicated in the following table : Length, mm. Length, mm. Dorsal rib No. I 659 Dorsal rib No. 8 660 + 2 885 9 633 3 861 10 532 4 912 11 3°4+ 5 950 " " "12 304 6 930 13 253 7 887 " " " 14 221 15 171 Both sternal bones (Fig. 14) were found in natural position with their inferior edges in contact. Each bone consists of a laterally compressed, shaft-like, upper portion and a broader, blade-like, lower part. The shaft, gradually thickening, is Pelvis Girdle 47 FIG. 14 — Left Eternal bone, ex- ternal view. One fourth natural size. continued downwards in the blade on the antero-exterior face of which it forms a distinct ridge. The pos- terior part of the blade is very thin and inclines inwards; therefore, it is not in the same plane as the laterally compressed shaft. The inner face is flatter than the outer in the shaft, and is slightly concave in the blade. The upper free end of the shaft is considerably expanded, particularly on the external side. The whole bone is slightly curved laterally and its anterior margin forms a sweeping concave curve. MEASUREMENTS OF STERNAL BONES Left Right mm. mm. Total length 365 348 Width of expanded upper end 88 90 Minimum width of shaft 39 41 Maximum thickness of shaft 20 Width of blade, diagonal 170 178 Thickness of blade at anterior ridge 45 Thickness of posterior part of blade 8 Pelvic Girdle and Hind Limbs The pelvic girdle (Fig. 15) conforms to the usual tracho- dont type and is to be distinguished chiefly by the character of the prepubis. The figure and the measurements given in the tables require little additional description. The ilium has the same general aspect as that of Clao- saurus annectens figured by Marsh, 1 or that of Stephanosaurus (Trachodon) marginatus, Lambe. 2 The preacetabular portion is much narrower than the posterior, is rather tapering, and somewhat decurved, with a thick and rounded upper margin. »i6th Ann. Rep., U.S. Geol. Sur., Plate LXXIII. 2 Con. Can. Pal., Geol. Sur. Can., Vol. Ill, Pt. II, p. 76. 4 8 Kritosaurus incurvimanus Above the ischiac peduncle the superior margin of the bone folds outwards in a broad shelf which is separated from a considerable rugose area above the peduncle by a pronounced longitudinal groove. The posterior blade-like portion reaches its greatest length near the inferior border. FIG. 15 — Risht pelvic girdle. About one fifteenth natural size. IL. ilium; P, pubis] PP. postpubis; IS. ischium. The pubis differs from that of other trachodonts in that the preacetabular portion or prepubis is more distinctly divisible into two parts: a proximal shaft-like section and a distal blade of which the inferior and superior margins are remarkably parallel. The width of the prepubis is less than usual, but its length is exceeded only by that of Traclwdon mirabilis; its anterior end is less rounded than in the case of most trachodont pubes. The inferior branch for union with the ischium is slender and the area of contact small. The postpubis is moderately long, relatively stout proximally, but thin and delicate towards the extremity where it is slightly expanded. The pubic notch, between the postpubis and the ischiac branch of the prepubis, is open and without any sign of being transformed into a foramen. The ischium is a longer and more robust bone than the pubis; its proximal portion is flat or slightly convex externally and with a pronounced inward direction ventrally. This portion bears a wide surface for union with the postace- tabular peduncle of the ilium, and a much narrower area for union with the pubis below the acetabulum. The superior margin of this proximal portion curves downwards and Hind Limb 49 backwards in a concave sweep passing gradually into the posterior shaftdike section. The inferior margin, also, is slightly concave from the union with the pubis backwards to FIG. 16 — A, right femur, external view, slightly restored; B, left femur, internal view, somewhat restored by comparison with left. One eighth natural size. gt, great trochanter; It, lesser trochanter; 3t, third trochanter; ic, inner condyle; oc, outer condyle. 50 Kritosaurus incurvimanus the distinct obturator process. Posterior to this process the inferior margin rapidly approaches the superior and passes likewise into the shaft-like portion. The elongated posterior part of the bone is flattened internally and is in contact with its fellow, almost, if not quite, as far forward as the obturator process. Externally it shows a rather sharp ridge a little ventral to the midline. The distal end is somewhat swollen, almost entirely on the ventral side. The femur (Figs. 16 and 17) consists of a comparatively light shaft and extremities so expanded that the bone has a clumsy appearance. On the internal side the shaft is evenly rounded, somewhat contracted towards the proximal end, and curved distinctly forwards and inwards where it expands into the large rounded head. As the left femur was much injured by erosion and as the head of the right is still buried in the acetabulum it is to be understood that the dimensions and shape of the head as shown in Fig. 16 are open to correction. Distally the shaft, seen from the internal side, maintains a fairly constant diameter until very near the end where it suddenly expands, much more posteriorly than anteriorly, into the very large inner condyle. This structure is com- paratively flat internally and shows distinct longitudinal fluting near the rounded articular surface. The external side of the shaft is less rounded and more flattened than the internal. Proximally there is a wide and thin expansion in the anterior position which is interpreted as the lesser trochanter although some authors would regard it as the greater trochanter. This flange-like extension con- tinues around the upper external face of the bone and down- wards on the postero-external side, there forming the greater trochanter. The two trochanters, therefore, lie almost in a plane on the external face of the bone; in fact, there is a slight concavity rather than a convexity between them, but it must be admitted that pressure may have affected the parts to some extent. The greater trochanter is thicker than the lesser and fades more gradually into the shaft internally. The proximal flange formed by the union of the Hind Limb 51 two trochanters overhangs the head and is separated from it by a pronounced wide and continuous concavity which is prolonged down the anterior side of the bone for a third of its length. On the external side the shaft swells distally into a large outer condyle which is similar in position and shape to the inner, and, like it, is longitudinally fluted. An outward deflection of the posterior part of the outer condyle produces a distinct concavity on the external face. The two condyles are separated by deep anterior and posterior de- pressions: the posterior is 65 mm. deep and is confired to the overhang- ing part of the condyles; the anterior is really deeper, perhaps as much as 85 mm., but as it is excavated in the distal end of the shaft proper and runs FIG . i 7 _Ri g ht femur, distal view. forward to the anterior margin, it is 0ne f hth n f. ural . 8ize : . oc, outer condyle; ic, inner less conspicuous from the distal condyle. point of view. Neither intercondylar groove is closed, but the anterior groove shows a tendency in this direction as a distinct prominence is developed on the inner condyle which is apposed to a still stronger inflection on the outer. The anterior sides of both condyles show fluting as in the case of the inner and outer faces. The third trochanter is a prominent, elongated, plate- like extension on the posterior side of the shaft at about its midlength. Its greatest width is 68 mm. at a point some- what below its centre. Owing to injury it is impossible to accurately describe this trochanter. The tibia (Fig. 18) is a shorter bone than the femur; it is contracted in the shaft but greatly expanded at both ends. The proximal expansion is nearly antero-posterior while the distal is almost at right angles to that direction. This twist occurs in such a manner that the inner face proximally becomes the posterior face distally. The proximal expanded end of the bone is thin anteriorly and turned outwards as a distinct enemial crest. On the 52 Kritosaurus incurvimanus outer face, posterior to this crest, is a wide shallow depression followed by a robust inner condyle which seems to have a backward direction. The proximal end of the fibula over- FIG. 18 — A, left tibia, interna] view; B, lisht tibia, external view. One eiyhtb natural size, i.e., inner condyle] o.c outer condyle; e.e., enemial crest; o.m., outer malleolus; i.m., inner malleolus. laps this condyle laterally. A second condyle, separated from the first by a deep intercondylar notch, forms the postero- lateral angle of the bone. Hind Limb 53 The large proximal expansion fades into the shaft in long sweep- ing curves of which the posterior is the more concave. The dis- tal expansion, from the outer viewpoint, shows a rather sharp edge running down to the ex- tremity of the elongated outer malleolus. The inner side of the bone shows the proximal expansion as a fairly flat surface turned sharply outwards at the enemial crest. The distal expansion, from this point of view, appears as a thicker and considerably shorter malleolus than the outer. Viewed from the posterior side the distal end of the bone shows the longer external and shorter internal malleoli separated by a shallow depression. The face of the bone, in this direction, shows a rather sharp median ridge which slopes away gradually to the margins. The fibula (Fig. 19) is a long and very slender bone, expanded proximally and rather less dis- tally; the two expansions are not quite in the same plane. The proximal end is convex externally and concave internally, the con- cavity extending half way down the shaft. The distal end is flattened and striated on the postero-internal face where it comes in con- tact with the tibia. FIG. 19 — Left fibula; A, external, proximal, and distal views; B, internal view. One eighth natural size. 54 Kritosaurus incurvimanus FIG. 20 — Right astragalus. A, external view; B, distal view. One fourth natural size. p, proximal; d, distal; ant. anterior; int. internal. Of the tarsal bones only the astragalus (Fig. 20) is known. This is a cap-like bone, hollowed proximally to fit over the inner malleolus of the tibia. There is an ascending point in front which fits in between the two malleoli and a more pronounced point behind the inner malleolus. The distal surface is well rounded antero-posteriorly, and is slightly con- cave laterally. In- ternally the surface slopes up to a rather sharp convex edge; externally the edge is thicker with a distinct articular surface for the calcaneum. The pes (Figs. 21 and 22, and Plate VI) is of the usual trachodont type and presents no unique features. All six metatarsal bones were found, but a few of the phalanges were missing. Only one bone was unrepresented in either one foot or the other — the first phalanx of the fourth digit. The metatarsals are all stout bones expanded at both ends. The middle bone is much longer and heavier than the other two of which the inner is the lighter. Metatarsal II is much flattened vertically and greatly expanded in this direction at the proximal end. The internal face is rather smoothly convex transversely and evenly concave longitudinally. The external face is quite flat proximally where it is in close contact with metatarsal III; distally, it diverges and is more irregular. The anterior edge is rather sharp and runs up to a decided point about 65 mm. from the beginning of the distal articular surface. The posterior edge is fairly sharp and evenly concave long- itudinally. The proximal articular surface is strikingly flat and is very elongate vertically and compressed laterally. The dis- tal articular surface is rhomboidal in outline with the upper Hind Limb 55 and lower sides of the rhombus inclined down and in. The articular facette is strongly convex above and concave transversely below. Metatarsal III is much the heaviest bone of the pes; it is stout and shaft-like at midlength but expands at both ends. The proximal expansion is sub-triangular with a flat base internally and a rounded apex externally. The distal expansion is quadrangular to sub-rhomboidal in outline. FIG. 21 — Right metatarsus, anterior and proximal views. One eighth natural size. II, second metatarsal; III, third metatarsal', IV, fourth metatarsal. FIG. 22 — Right metatarsus, posterior and distal views. One eighth natural size. II, second metatarsal; III, third metatarsal; IV, fourth metatarsal. The external aspect shows a distinct concavity in the distal expansion between the upper and lower margins. Proximally this depression passes into a distinct ridge which becomes the rounded apex of the sub-triangular head. The internal face is rather flat at the distal end and convex at midlength. Proximally it forms a broad flat triangle in a plane inclined upwards and outwards. This surface fits closely against the corresponding flattening on Metatarsal II. 56 Kritosaurus incurvimanus The distal articular surface is continued well up on the anterior face; it is convex vertically and slightly concave laterally. The proximal articular surface is flat and sub- triangular in outline. Metatarsal IV is a bone of very irregular shape, flattened dorso-ventrally in the shaft and expanded at both ends. The distal expansion is sub-rhomboidal and concave on all four sides; the internal concavity is deepest and sharpest causing lip-like tuberosities in the anterior and posterior positions. The external and posterior concavities are shallow and broad, and the anterior is but slightly developed. Proximally the bone expands evenly on the anterior, posterior, and external sides rising to a rather sharp edge against 'the articular surface. Internally it is strongly excavated in a broad hollow which fits over the rounded apex of the triangular head of the third metatarsal. The floor of this hollow runs out on the internal side of the bone into a conspicuous roughened point a little above mid- length. The proximal articular surface is slightly concave and sub-triangular to sub-quadrate in outline. The base of the triangle is internal and concave; the apex is external and very broadly rounded. The distal articular surface is rhomboidal in outline with concave sides; it is strongly convex dorso-ventrally and slightly convex laterally. The phalangeal formula is the same as in other members of the Trachodontidae as follows : Digit II with three phalanges, the third a hoof. Digit III with four phalanges, the fourth a hoof. Digit IV with five phalanges, the fifth a hoof. Plate VI and the table of measurements require no additional description in the case of these small bones. Pelvis Girdle 57 COMPARATIVE MEASUREMENTS OF PELVIC GIRDLE AND HIND LIMBS 1 I II III IV V VI VII mm. mm. mm. mm. mm. mm. mm. Ilium — Total length 1013 1160 1030+ 1150 1035 1060 Preacetabular border to ant. end 430 480 410 470 Width at pubic peduncle . 215 205 32o(? Maximum width of ant. ramus 68 Average width of posterior blade 117 Pubis — Total length 1038 1150 630 1000 940 Width of blade of pre- pubis 163 310 200 220 270 Minimum width of pre- pubis 90 100 92 120 Length of prepubis 519 590 360 450 490 485 Length of postpubis , from notch 532 Width of distal part of postpubis 25 Minimum thickness of postpubis 8 Width of terminal swelling 25 Thickness of terminal swelling 17 Ischium — Length, distal end to pubic union 1026 1200 1090 1030 1140 Length, distal end to iliac union 988 1050 Across iliac and pubic heads 240 34° Distal end to obturator process 873 Width at obturator pro- cess I2 ° Lateral thickness of distal swelling 65 Tor explanation of the numbers above the columns see page 41. 58 Kritosaurus incurvimanus Comparative Measurements of Pelvic Girdle and Hind Limbs — Cont. ^^^^^^^ ~i il m iv v vi vTT mm. mm. mm. mm. mm. mm. mm. Ischium — Dorso- ventral thickness of distal swelling 62 Minimum girth of the two ischia where united 177 Girth of the two distal swellings 305 Femur — Length, outer condyle to proximal end 1045 1150 1040 1170 1080 1182 Length, inner condyle to head 1014 1 169 Breadth of upper ex- tremity 209 246 Antero-posterior diameter of inner condyle 292 300 Antero-posterior diameter of outer condyle 262 Thickness at condyles 210 Middle of inner condyle to tip of third tro- chanter 504 Thickness of shaft below head 90 Tibia — Total length 943 1020 870 1000 1000 1018 1080 Width of proximal expan- sion 326 350? 310 272 Minimum diameter of shaft 87 Width of distal expansion . . 270 337 Thickness of inner condyle.. 134 Thickness of inner malleolus 88 Thickness of outer malleolus no Fibula — Length 878 970 820 920 950 1000 Width of proximal expan- sion 153 190 160 Width of distal expansion . . 112 125 55 Girth, 300 mm. from lower end 143 Girth, 300 mm. from upper end 193 Hind Limb 59 Comparative Measurements of Pelvic Girdle and Hind Limbs — -Conl. I II III IV V VI Vl T~ mm. mm. mm. mm. mm. mm. mm. Fibula — Thickness of proximal expan- sion 53 Thickness of distal expansion 70 Astragalus — Width, lateral 167 Length, antero-posterior — 213 Greatest thickness 45 Metatarsals' — Metatarsal II, length 281 280 280 280 310 350 " " vertical dia- meter dis- end 135 " " transverse diameter distal end 79 no 100 " "vertical diameter proximal end- 166 " " transverse diameter proximal end 68 no 90 Metatarsal III, length 363 420 340 370 380 430 " " vertical dia- meter dis- tal end . . 89 " " transverse diameter distal end 124 170 130 130 ' " vertical diameter proximal end 165 " transverse diameter proximal end 83-95 180 100 140 " " minimum girth 232 6o Kritosaurus incurvimanus Comparative Measurements of Pelvic Girdle and Hind Limbs — Cont. I II III IV V VI VII mm. mm. mm mm. mm. mm. mm. Metatarsal IV, length 278 330 275 300 320 340 " vertical diameter distal end 89 " transverse diameter distal end 80 no 120 " oblique diameter distal end 173 " vertical diameter proximal end 112 " transverse diameter proximal end 84 85 100 " minimum girth 195 I II III IV V VI VII mm. mm. nm. mm. mm. mm. mm. Phalanges — II 1 length 130 130 130 120 140 " proximal transverse width... . no " proximal vertical width. 82 " distal vertical width .... 53 " minimum girth 102 IP length 47 70 55 60 45 " proximal transverse width... . 75 " distal transverse width . proximal vertical width . 70 50 " " distal vertical width .... 35 " girth at middle 175 IP length 80 80 no 85 " proximal transverse width... . 58 " width of hoof 58 44 ■■ proximal vertical width . Hind Limb 6i Comparative Measurements of Pelvic Girdle and Hind Limbs — Cont. I II III IV V VI VII mm. mm. mm. mm. mm. mm. mm. Phalanges — III 1 , length 118 140 120 130 135 " proximal transverse width.. . . 140 ' ' distal transverse width 114 ' ' proximal vertical width 82 " distal vertical width 55 " minimum girth 262 IIP, length 33 60 50 40 40 " proximal transverse width.. . . no " distal transverse width no " proximal vertical width 58 " distal vertical width 45 III 3 , length 25 50 40 40 25 " transverse width 90 ' ' proximal vertical width 43 " distal vertical width 40 III 1 , length 80 100 100 100 90 " proximal transverse width... . 76 " proximal vertical width 40 " width of hoof 103 " girth above hoof 152 IV 1 , length no 90 95 no IV 2 , length 20 40 30 25 25 " transverse width 71 " vertical width 50 IV 3 , length 18 30 20 22 20 " transverse width 70 " vertical width 50 IV 4 , length 14 45 3° 25 17 " transverse width 63 " vertical width 38 IV 6 , length 85 100 90 105 95 " proximal transverse width... . 55 " proximal vertical width 44 " width of hoof 73 " girth above hoof 126 62 Kritosaurus incurvimanus Musculature The ossified tendons of muscles so characteristic of this type of dinosaur are preserved in unusual perfection along the vertebral column from the fourth dorsal to the nine- teenth caudal vertebra. In all, 93 muscles were observed; but it is probable that this number would be increased, even in the part of the animal preserved, if the tendons lost or hidden in the matrix were added. The drawing, Plate I , shows with reasonable accuracy the course and position of the tendons actually observed, with- out any attempt at restoration. The necessity of leaving some matrix for the support of the outer muscles and some patches of skin which it was thought advisable to retain has interrupted the continuity of the muscles in certain cases. The tendons are round or slightly oval in the major part of their length, and, on the average, are about 7 mm. in diameter; they become thin and wide towards the ex- tremities, in some cases reaching a diameter of 18 mm. While these flattened extremities are in some cases closely applied to the neural spines, in others they cease a little short of the spine to which they belong. It is likely that the actual connection was effected by short unossified endings. The muscles are arranged in three major divisions which I propose to indicate as "sets"; the sets are divisible into "groups," and in one instance the group is resolved into "series." The anterior ends are regarded as the "origins," and the posterior ends as the "insertions." D, S, and C are used to designate dorsal, sacral, and caudal vertebrae respectively. The number following the letter indicates the position of the vertebra in the series to which it belongs. In the following tables the muscles are numbered in sets, thus "III4" is the fourth muscle of the third set. The second column in the tables indicates the actual, observed extent of the tendon; the third column shows the probable extent which is deduced from the observed extent of the more perfect tendons of the group in question ; the fourth column shows in millimetres the length of the part actually visible. Muscles 63 muscles of set i The first set includes all those muscles which extend backwards and downwards from near the summits of the neural spines. These tendons underlie all others and with a few exceptions are closely applied to the sides of the neural spines throughout their whole extent. Thirty-six muscles are included here although five of them are inferred rather than observed in position. The anterior members of the set are of medium length, those of the middle region are somewhat longer, and the posterior members are much shorter and more highly inclined. Two groups can be distinguished — an anterior group of longer tendons and a posterior group of shorter tendons. The latter does not follow the former in regular order but the two groups over- lap in the posterior part of the sacral region. The first group is capable of an indistinct division into two series — an anterior regular series, and a posterior series of less regular development. Set I, Group 1, Series 1. There are eleven, or possibly twelve, muscles in this series. The insertions of the first four can not be seen owing to a patch of skin which covers them. The last tendon of the series could, with equal reason, be placed in the second series. Calculated from the more perfect muscles observed, the average length is 554 mm. Each tendon stretches across seven neural spines inclusive and is closely applied to the sides of the spines throughout its whole length. 6 4 Kritosaurus incurvimanus TENDONS OF SET I, GROUP 1, SERIES 1 Observed Probable Observed No. Notes range true range length, mm. I i D 4 -.. D 4— Dio 40 Covered distally I 2 D 5-.. D 5— Dn 30 " " I 3 D 6—.. D 6— D12 20 ii it I 4 D 8—.. D 7— D13 Broken anteriorly I 5 D 8— D14 D 8— D14 560 I 6 D 9— D14 D 9— D15 450 Broken posteriorly I 7 Dio— D16 Dio— D16 570 I 8 Du— Si Du— Si 560 I 9 D12— S2 D12— S2 530 I 10 D13— S3 D13— S3 545 I ii D14 — S4 D14 — S4 560 I 12 D15-S5 D15-S5 625 Might go to Series 2 Set 1, Group 1, Series 2. This series begins with some very long members which diverge distally from those of Series 1 and are inserted nearer to the bases of the neural spines. The posterior members of the series are irregular, shorter, and probably not inserted on the neural spines distally, they lie between some of the anterior tendons of Group 2. TENDONS OF SET I , GROUP 1, SERIES 2 No. Observed Probable Observed range true range length, mm. Notes 1 13 DI6— S7 D16— S7 700 1 14 Si— Ci Si— Ci 870 1 15 S7-C3 S7-C3 435 1 16 C2— C7 S9-C7 350 Inserted on transverse process of c 7 Set 1, Group 2. This group of tendons begins with some very small members in the sacral region ; the origins are to be seen but the insertions are hidden under the muscles of Set II. The posterior muscles are heavier, but, in most cases, neither the origin or insertion is clearly seen. Muscles 65 There is little doubt, however, that all the muscles of the group extend across four spines inclusive with a length of 300 to 400 mm. In the part of the animal preserved there are fifteen of these tendons, but as five more were in all probability present they are included in the table, making 20 in all. TENDONS OF SET I, GROUP 2 Observed Probable No. range true range Length Notes I 17 S3-S4 S2-S5 Hidden distally I 18 S4— S5 S3— S6 Hidden distally I 19 S4— S7 S4-S7 I 20 S6— S7 S5— S8 I 21 S6— S7 S6—S9 I 22 S6— S7 S7— Ci I 23 S8— C2 S8— C2 300 I 24 C2-C3 S9-C3 1 25 C3— C 4 Ci— C4 I 26 c 4 — ... C2— C5] [ \ I 27 C5— . . . C3— C6 J- J All hidden anteriorly under 1 I 28 C6— . . . C4-C7J muscles of Set II 1 I 29 C5— C8 Lost entirely I 30 C6— C9 Lost entirely I 3i C8— Cio C7— Cio I 32 C8— C9 C8— Cn I 33 C9 — C12 Lost entirely I 34 Cio — C13 Lost entirely I 35 Cn— C14 The broken piece on C9 pro- bably represents one of these lost tendons. I 36 C13- C12— C15 MUSCLES OF SET II This set includes all those tendons which run backwards and upwards to insertions on the sides of the neural spines near their summits. Such insertion is observed on every neural spine from D7 to C19 leading to the conclusion that these tendons were regularly developed, one for each spine, over the 30 vertebrae in question. The anterior ends seem to be less regular and as they are more affected by distortion it is difficult to state their exact limits; nevertheless, it is 66 Kritosaurus incurvimanus reasonably certain that the origins of the more anterior members are on the transverse processes and that distally there is an increasing tendency for them to be situated on the neural spines. In no case was a muscle seen to actually arise from a transverse process; it must be admitted, there- fore, that the free and irregular anterior endings may be entirely due to the tendons having been torn away from a normal origin near the base of the neural spines. According to the location of the origin it is possible to divide the set into seven groups to which may be added an eighth to include a single abnormal tendon. Excepting this one, all the tendons are external to those of Set I. Set II, Group 1. Nine tendons are included in this group; they are all to be seen at their posterior ends, but only in the case of the last two could the origin be made out with certainty. These extend over nine spines with the origin apparently on the transverse process. The assumption of a similar origin and extent for the first seven is scarcely justified but this pro- cedure has been followed in making the table below. It will be observed also that the probable insertion is given in each case on the spine posterior to the observed insertion; this was found to be necessary in order to preserve the continuity of the group and it is thoroughly justified by the fact that some of the posterior ends actually overhang distally the spines to which direct observation would credit them. TENDONS OF SET II, GROUP 1 Observed Probable Observed No. Notes range range length, mm. II i — D6 Di— D7 400 II 2 -D 7 D2— D8 400 II 3 — D8 D3— Do 400 II 4 -D 9 D4— Dio 300 II 5 D 5— Dio D5— Dii 400 II 6 Dio— Dn D6— D12 150 II 7 Dio— D12 D 7 — D13 200 Under patch of skin II 8 D 6— D13 D6— D14 775 II 9 D 7— D14 D7r-Di5 690 Muscles 67 Set II, Group 2. This group consists of only one muscle which differs from all others of the set in that it lies internal instead of external to the tendons of Set I. Further the origin seems to be on a neural spine near its base instead of on the transverse process as in the case of Group 1 . TENDON OF SET II, GROUP 2 No. Observed range Probable Observed true range length, mm. Notes II 10 Dn— D14 Dn— D16 Origin low on spine Set II, Group 3. Each of the ten tendons of this group extends across seven neural spines. The anterior ends are divergent and the origins are well down on the spines; the posterior parts are close together and almost parallel with one another. The average length, calculated from the more perfect tendons only, is 623 mm. TENDONS OF SET II, GROUP 3 Probable true range Observed length, mm. Dn — Si 625 D12— S2 505 D13— S3 610 D14— S4 450 D15— S5 220 D16— S6 636 Si— S 7 485 S2 — S8 460 S3— So 535 S4 — Ci 470 Set II, Group 4. The tendons of the fourth group resemble those of the third in having both the origins and insertions on the sides of the neural spines and in diverging anteriorly; they differ in extending across nine spines instead of seven with a consequent greater length, probably 800 mm. No. Observed range II 11 Dn— Si II 12 D12— Si II 13 D13— S3 II 14 D15— S 4 II 15 S3 -S 5 II 16 D16— S6 II 17 Si— S6 II 18 S2— S7 II 19 S3— S8 II 20 S5— S9 68 Kritosaurus incurvimanus TENDONS OF SET II, GROUP 4 „ T Observed Probable Observed ,. No. , . Notes range true range length, mm. II 21 S4 — Ci S5 — C2 775 Evidently longer II 22 S4 — C3 S4 — C3 800 II 23 S5 — C3 S5 — C4 720 Evidently longer Set II, Group j . The tendons of this group differ in that they extend across ten spines. The anterior member is very long as its origin is low down on the broad sacral spine. TENDONS OF SET II, GROUP 5 „. Observed Probable Observed ... No. , , Notes range true range length, mm. II 24 S 5 — C5 S 5 — C 5 835 II 25 S6— C6 S6— C6 735 II 26 S7— C7 S7— C7 730 Set II, Group 6 . The five muslces of this group have an average length of 647 mm. and extend over nine spines. They differ also in that they are approximately parallel and close together throughout their course; in consequence, the origins are higher up on the spines. The last member, however, is separated by a considerable interval from the rest. TENDONS OF SET II, GROUP 6 No. Observed range Probable true range Observed length, mm. Notes II 27 C4— C8 So— C8 310 Ant. end hidden II 28 Ci— Co Ci— Co. 660 II 29 C2 — Cio C2 — Cio 660 II 30 C3-C11 C3— Cn 645 II 31 C4 — C12 C4 — C12 626 Muscles 69 Set II, Group 7. ^ The tendons of this group seem to extend across seven spines. The anterior ends are very differently situated from those of the previous group as they are free from the spines with the origins possibly on the dorso-lateral sides of the vertebrae. As the origins were in no case actually seen it may well be that the unusual position of the anterior ends is due to the tendons having been torn away from a more normal attachment on the spines. TENDONS OF SET II, GROUP 7 XT Observed Probable Observed No. Notes range true range length, mm. II 32 C7— C13 C7-C13 600 Origin well in on arch II 33 C8— C13 C8— C14 580 Origin farther out on arch II 34 C9 — C14 Co— C15 410 Origin still farther out on arch Set II, Group 8. As in the last group the tendons extend over seven spines but the origins are again low down on the sides of the spines. TENDONS OF SET II, GROUP 8 No. Observed range Probable true range Observed length, mm. II 35 II 36 II 37 II 38 Cio— C14 C12— C14 C13— C14 Cio— C16 Cii— C17 C12— C18 C14 — C19 290 120 60 MUSCLES OF SET III The muscles of this set are developed in connection with the ilium and the transverse processes of the vertebrae; in a few cases only is the insertion so far in that a connection with the neural arch or the base of the spine is suggested. Few, if any, of these tendons show both origin and insertion; their tortuous course, likewise, indicates displacement and 70 Kritosaurus incurvimanus renders their original position difficult to determine. The set is divisible into three groups : an anterior group associated with the transverse processes of the anterior dorsal vertebrae, a second group extending backwards from the transverse processes of the posterior dorsal vertebrae to the superior margin of the ilium, and a third or posterior group arising either from the end of the ilium or from transverse processes in the vicinity and stretching backwards to the transverse processes of the caudal vertebrae. Set III, Group 1. Five muscles were observed in this group ; they run from the transverse processes backwards. The anterior members are inserted on their respective vertebrae in the angle at the base of the neural spine, thus merging into the first group of the second set. The posterior members are inserted farther out, on the dorsal aspect of the vertebrae or well in on the transverse processes. While rather un- certain, on account of the doubtful insertions, it is likely that each tendon extends across six vertebrae inclusive, with an average length of about 400 mm. TENDONS OF SET III, GROUP 1 .. Observed Probable Observed - T JNo INotes range true erang length, mm. Ill I D7 — D12 D7 — D12 390 Origin on side of trans, proc. Insertion on neural arch? Ill 2 D8 — D13 D8 — D13 460 Origin near tip of trans, proc. Insertion on neural arch? Ill 3 D9 — D14 D9 — D14 420 Origin near tip of trans.proc. Insertion on dorsal side of vertebra. Ill 4 Dn — D15 Dio — D15 370 Origin near tip of trans, proc. Insertion on dorsal side of vertebra III 5 D12 — D16 Dn — D16 370 Origin near tip of trans, proc. Insertion on base of trans, proc. Muscles 71 Set III, Group 2. Each of the six tendons of this group arises near the extremity of the transverse process to which it belongs. The anterior two seem to be inserted on transverse processes ; the posterior four are inserted close together in a groove on the superior edge of the ilium over the fourth and fifth sacral vertebrae. TENDONS OF SET III, GROUP 2 ,., Observed Probable Observed No. Notes range true range length, mm. I 6 D13— D13— S2orS3 I 7 D13— S3 D13— S3orS4 410 I 8 D14 — S5 D15 — S5 410 Inserted on ilium I 9 D15 — S5 D15 — S5 390 Inserted on ilium I 10 D16 — S5 D15 — S5 365 Inserted on ilium I II — S5 D16 — S5 Beneath others at insertion on ilium Set III, Group 3. The tendons of the third group terminate anteriorly in a very hard matrix which leaves their point of origin in great doubt. The general course, however, is suggestive of an origin on the posterior border of the ilium or far out on the transverse processes of the posterior sacral vertebrae. The tendons are long and more slender than those of the other sets ; they seem to have a range over ten vertebrae and to be inserted on the transverse processes of the caudal vertebrae. TENDONS OF SET III, GROUP 3 Observed Probable Observed , T . No . , .Notes range true range length, mm. I 12 S9 — C4 "*" S4 — C4 350 Anterior end lost I 13 S9 — S5 S5 — C5 400 Anterior end lost I 14 S6— C6 S6— C6 700 I 15 S 7 — C 7 S 7 — C7 680 I 16 S8— C8 S8— C8 640 I 17 Ci— C9 Ci— C9 600 72 Kritosaurus incurvimanus In addition are two tendons which do not fall easily into any of the groups: the first of these might be ascribed to Set III, Group 3, and the second to Set II, Group 7. The first appears in the matrix outwards from the neural spine of Ci and extends to about half way up the neural spine of C5, 330 mm. The second seems to arise from the transverse process of C6 and to reach the neural arch of Co, 210 mm. The tendon was probably much longer posteriorly. Integument Many skeletons of trachodont dinosaurs are accompanied by impressions which accurately portray the character of the epidermal covering. The most famous of these discoveries is the "dinosaur mummy," a skeleton of Trachodon annectens in which the greater part of the epidermal structure is revealed. This skeleton has been described in detail by Dr. Osborn. 1 Lambe, also, has described and figured a number of skin impressions from the Cretaceous rocks of Alberta. 2 Regarding Trachodon annectens Dr. Osborn states : ' ' Pro- perly speaking the skin is not squamate, or imbricating, as in the lizards, but is rather tuberculate. ... In all parts of the the body where the impressions are preserved, the epidermis was evidently covered with a pattern composed solely of tubercles, which were mainly of two kinds: (1) Small, rounded tubercles = ground plan, uniformly distributed. (2) Large 'pavement' tubercles, irregularly pentagonal in out- line = raised pattern, diversely distributed." Both Osborne and Lambe hold the opinion that these epidermal impressions are distinctive for each species and that they will eventually prove of the greatest service in the practical identification of specimens. Impressions of the skin of Kritosaurus incurvimanus (Plate VII) were observed in the following regions: (1) Cer- vical, (2) Scapular, (3) Mid-rib, (4) Dorsal spines 7 to 9, (5) Dorsa l spines 14 to 17. 'Integument of the Iguanodont Dinosaur Trachodon, Henry Fairfield Osborn, Mem., Am. Mus. Nat. Hist., New Series, Vol. 1, Part II. 2 0ttawa Naturalist, Vol. XXVII, No. 10. Integument 73 ( 1) The skin on the under side of the neck has been thrown into folds the impressions of which are very indistinctly pre- served over a length of about 18 inches. Throughout this area no trace of pattern could be seen, all the tubercles being of polygonal outline, somewhat variable in size but occurring to an average number of three in the space of ten milli- metres. These impressions had to be sacrificed in order to expose the cervical vertebrae. (2) A small patch of skin at about mid-length of the scapula shows the same sort of ground plan, but the tubercles are uniformly smaller, occurring to the number of four in the space of ten millimetres. (3) Several small patches of skin are preserved in the mid-rib region. They all show tubercles of about five millimetres in diameter, with deeply impressed, somewhat sinuous, polygonal boundaries. Among these larger tubercles are scattered a few smaller ones without any sign of regular arrangement. At intervals varying from 40 to 60 mm. occur sub-conical elevations measuring 12 mm. by 15 mm. (Raised pattern of Osborn, limpet-like elevations of Lambe.) The little cone is made up of about twelve convex sections which converge to a rounded apex. Surrounding the elevation is a ring of ten of the ordinary tubercles. (4) A patch of skin over the neural spines of dorsal vertebrae seven to nine shows a ground plan of tubercles like that of the mid-rib region but somewhat finer, as 2.5 to 3.5 tubercles occur in the space of 10 mm. The limpet-like elevations occur here, likewise, and the general appearance is very like that figured by Lambe for the caudal region of Stephanosaurus marginatus (Plate XVI, op. cit.). In the dor- sal region of Lambe's species the limpets are very much larger. (5) Covering the neural spines of dorsal vertebrae four- teen to seventeen is a well preserved patch the ground plan of which is very like that of the more anterior dorsal region described above. Here, however, there seems to be none of the limpet-like elevations, but other dermal structures are developed which are different from anything hitherto ob- served in a trachodont dinosaur. 74 Kritosaurus incurvimanus Along the median line of the back are conspicuous dermal elevations comparable in structure to the raised elements in the patches of skin already described; they are, however, of such great size as to assume the character of special dermal callosities. Two of these structures, and part of a third, are preserved, indicating that a row of them extended along the back, at least in the dorsal region. The best-preserved callosity is situated above the fifteenth and sixteenth dorsal spines; it is 125 mm. long, 60 mm. high, and probably 50 or 60 mm. thick. From its posterior edge to the similar edge of the next callosity distal to it is 2 10 mm. indicating that there is no relation between the callosities and the spines. The ordinary skin continues across the median line of the back between the callosities but it termin- ates against the base of the callosity in a sharply defined, infolded line. These peculiar elevations resemble low, laterally com- pressed cones with the apex posterior to the middle. The sides of the cones are vertically fluted in a manner to suggest that the flutings represent elongated tubercles of about the same diameter as those of the neighbouring skin. Towards the apex the flutings merge into a tuberculate surface not unlike that of the ground plan. INDEX Astragalus 54 Astragalus, measurements of 59 Atlas 23 Axis 24 Basioccipital 15 Basioccipital, measurements of . . . 22 Basipterygoid process 19 Basisphenoid 17 Carpals 37 Caudal vertebrae 29 Cervical ribs 44 Cervical vertebrae 25 Cheneosaurus 9 Chevrons 31 Claosaurus 9 Claosaurus annectens 10, 36, 41, 47, 72 Coracoid 33 Coracoid, measurements of 42 Corythosaurus 9, 41 Description, detailed 11 Description, general 7 Diclonius 9 Discovery 5 Dorsal ribs 46 Dorsal vertebrae 26 Edmontosaurus 9 Exoccipital 15 Femur 50 Femur, measurements of 58 Fibula 53 Fabula, measurements of 58 Frontal 12 Frontal, measurements of 22 Gryposaurus notabilis 7, 9 Hadrosauridae 9 Head 11 Head, measurements of 21 Humerus 34 Humerus, measurements of 42 Hypacrosaurus 36, 41 Hypocentrum 23 Ilium 47 Ilium, measurements of 57 Integument 72 Ischium 48 Ischium, measurements of 57 Jugal 14 Jugal, measurements of 22 Kritosaurus novajovius 7, 9 Lachrymal 12 Lachrymal, measurements of 21 Mandible 20 Mandible, measurements of 23 Manus 38 Manus, measurements of 43 Manus, phalanges of, 40 Manus, phalanges, measurements of 44 Maxillary 15 Metacarpals 39 Metacarpals, measurements of. . . . 43 Metatarsals 54 Metatarsals, measurements of . . . . 59 Musculature 62 Nasal 11 Nasal, measurements of 21 Odontoid 23 Orbitosphenoid 18 Orbitosphenoid, measurements of 22 Parapophyses sacral 28 Parasphenoid 18 Parasphenoid, measurements of. . . 23 Parietal 13 Parietal, measurements of 22 Pelvic girdle 47 Pelvic girdle, measurements of . . . 57 Pes 54 Pes, phalanges of 56 Pes, phalanges of, measurements . . 60 Phalanges of manus 40 Phalanges of manus, measurements of 44 Phalanges of pes 56 Phalanges of pes, measurements of 60 Position of bones as found 6 Postfrontal 13 Postfrontal, measurements of 22 Prefrontal 12 Prefrontal, measurements of 22 Premaxillary 12 Preparation 6 Presphenoid 19 Prootic 17 Prosaurolophus 9 Pterygoid 19 Pterygoid, measurements of 23 Pubis 48 Pubis, measurements of 57 Quadrate 14 Quadrate, measurements of 22 Quadrato-j ugal 14 Quadrato-jugal, measurements of. 23 Radius 36,37 Radius, measurements of 43 Ribs 44 Ribs, cervical 44 Ribs, dorsal 46 Sacral parapophyses 28 Sacral vertebrae 27 Sacrum 27 Saurolophus 9, 36, 41, 42, 44 Scapula 31 Scapula, measurements of 41 Shoulder girdle 31 Squamosal 13 Squamosal, measurements of 22 Stephanosaurus marginatus. .9, 36, 73 Sternal bones 46 Supraoccipital 17 Supraoccipital, measurements of . . 22 Teeth 20 Tibia 51 Tibia, measurements of 58 Trachodon mirabilis 38, 41 Trachodontidae, discussion of ... . 8 Ulna 39 Ulna, measurements of 43 Vertebrae, caudal 29 Vertebrae, cervical 25 Vertebrae, dorsal 26 Vertebrae, sacral 27 Vertebral column 23 PLATE I. Plate I.— KriTOSAURUS INCURVIMANUS. This figure indicates the position of the various parts of the skeleton as found, except that the hones of the hind limbs have been assembled. Xo bones have been restored except where necessary to show connections and such bones are dotted. Parts of the vertebral column hidden in the matrix have been drawn in provisionally. The n >ire is dcsiqin c^jHTjshow the relation of the various parts an 1 the musculature. Great accuracy in the individual bones has not been attempted. About one-fifteenth natural size. Hangf ^ aj O E 3 XS O u a -a ID CJ .M > PLATE III, FIGURE 1. PLATE III, FIGURE Plate III. — Kritosaurus incurvimanus. F.'gure 1, right side of head, one- sixth natural size; Figure 2, left side of head with temporal arches, jugal, etc., removed; one-fourth natural size: a, foramen for blood vessel; 1), foramen for blood vessel; A, articular, Boc, basioeeipilal; Boc. Tub, basioeeipilal tubercle; Bpt.Pr, basipterygoid process of basi- sphenoid; D, dentary; F, frontal; Fe. ov, fenestra ovalis; J, jugal; L, lachrymal; Mx. and M, maxilla; N, nasal; OSP, orbitosphenoid; P and Pa, parietal; P. P., pa raoccipital process; Pa. sp, parasphenoid; Pf, postfrontal; Pre. f and Prf, prefrontal; Pm, premaxilla; Pre. sp presphenoid; PI. Pt, palatal portion of pterygoid; Q, quadrate; Qj, quadrato-jugal; R. Pt, right pterygoid; R.Q, n'g/i/ quadrate; S, squamosal; Sa, surangular; II to XIII, Htrz'e foramina. PLATE IV, FIGURE 1. PLATE IV, FIGURE 3. PLATE IV, FIGURE 2. Plate IV. — Kkitosaurus incurvimanus. Figure 1, right half of head viewed from above, one-fourth natural size; Figure 2, posterior view of head, one-fourth natural size; Figure 3, mandibular tooth, twice natural size: b.p, bast pterygoid process of basis phencid; c, occipital condyle; Eco, exoccipital; F, frontal; f.m, foramen magnum; J, jiigal; L, lachrymal; N, nasal; P, parietal; Pt, pterygoid; Pf, postfrontal; Prf, prefrontal; PoP, paraoccipilal process; Pm, premixilla; Q, quadrate; Qj, quadrato-jugal; S, squamosal; t, basioccipital tubercle. PLATE V, FIGURE 1. £*a V V - 1 - c PLATE V, FIGURE 2. Plate V. — Kritosaukus incurvimanus. Dissociated phalanges of left nanus; Figure 1, anterior view; Figure 2, posterior view. One-third natural size. PLATE VI, FIGURE 1. PLATE, VI FIGURE 2. Plate VI. — Kritosaurus incurvimanus. Dissociated phalanges of right pes; Figure 1, anterior view; Figure 2, posterior view. One-fourth natural size. *- dp. PLATE VII, FIGURE ■■' ' ' '.'. ■ ~!"% w: -:.?*&&>• *i~ ;•:-- $&&L -:#'■'#>■; TMBi* 4 V:* ,/'■ '->'; iS^BSfii PLATE VII, FIGURE Plate VII. — Kritosaurus incurvimanus. F'gure 1, median dermal callosity above the fourteenth and fifteenth dorsal spines. One-half natural size. Figure 2, skin impression over the seventh and eighth dorsal spines. Natural size UNIVERSITY OF TORONTO STUDIES Geological Series. No. i : The Huronian of the Moose River basin, by W. A. Parks $0.50 No. 2 : The Michipicoten iron ranges, by Professor A. P. Coleman and W. A. Willmott 1.00 No. 3 : The geology of Michipicoten Island, by E. M. Burwash loo No. 4 : The stromatoporoids of the Guelph formation in Ontario, by Professor W. A. Parks 1.00 No. 5: Niagara stromatoporoids, by Professor W. A. Parks 1.00 No. 6 : Silurian stromatoporoids of America, by Professor W. A. Parks 1.00 No. >j : Ordovician stromatoporoids, by Professor W. A. Parks 1.00 No. 8 : A Cervalces antler from the Toronto Interglacial, by Professor B. A. Bensley 0.25 No. 9: Palaeozoic fossils from a region southwest of Hudson Bay, by Professor W. A. Parks 1.00 No. 10: Mineralogy of the H. B. Mine, Salmo, B.C., by Professor T. L. Walker 0-50 No. 11; The osteology of the trachodont dinosaur Krito- saurus incurvimanus, by Professor W. A. Parks 1.00 PftMPHUT BINDER • Syracuse, N. Y. I Stockton, Calif-