PLEASE HANDLE WITH CARE University of Connecticut Libraries 3 =1153 GAYLORD RG JNDIAN NOTES E AND MONOGRAPHS 5!^ Edited by F. W. Hodge ,f\^?6? .)! 45 A SERIES OF PUBLICA- TIONS RELATING TO THE AMERICAN ABORIGINES MORPHOLOGICAL AND METRL 11 CAL VARIATION IN SKULLS FROM SAN MIGUEL ISLAND, CALIFORNIA II. THE FORAMEN MAGNUM: SHAPE, SIZE, CORRELATIONS BY BRUNO OETTEKING NEW YORK MUSEUM OF "THE AMERICAN INDIAN J HEYE FOUNDATION 1928 LANCASTER PRESS, INC. LANCASTER, PA. MORPHOLOGICAL AND METRICAL VARIATION IN SKULLS FROM SAN MIGUEL ISLAND, CALIFORNIA II THE FORAMEN MAGNUM: SHAPE, SIZE, COR- RELATIONS BY BRUNO OETTEKING Digitized by the Internet Archive in 2011 with funding from LYRASIS members and Sloan Foundation http://www.archive.org/details/morphologicalmetOOoett CONTENTS 1. Introduction 7 2. Problem 8 3. Shape of Foramen Magnum 9 4. Metrical Definition of Foramen Magnum 16 a. Length 16 b. Width. 17 c. Length-width index 18 d. Module 20 e. Angular Relation to Ear-eye Plane 21 5. Correlations 24 a. Mutual Relation between Absolute Cranial and Foramen Magnum Measure- ments 25 a. Cranial Length and Foramen Mag- num Length 25 /?. Cranial Breadth and Foramen Mag- num Width 29 b. Mutual Relation between Proportional Evaluations 32 a. Cranial Length-breadth Index and Foramen Magnum Index 32 /3. Cranial and Foramen Magnum Mod- ules 35 c. Mutual Relation between the Foramen Magnum Angle and Absolute and Proportional Foramen Magnum and Cranial Evaluations 37 a. Angle and Length of the Foramen Magnum 37 /3. Angle and Index of the Foramen Magnum 40 y. Foramen Magnum Angle and Cranial Length 42 8. Foramen Magnum Angle and Cranial Length-breadth Index 44 6. Conclusion and Summary 47 7. Literature 54 MORPHOLOGICAL AND METRICAL VARIATION IN SKULLS FROM SAN MIGUEL ISLAND, CALIFORNIA II. The Foramen Magnum: Shape, Size, Correlations By Bruno Oetteking 1. INTRODUCTION THE following study represents the second in- vestigation of a series of skulls from San Miguel island, California, the more complete data of which may be found in the introduction to the author's first paper in this series on the Sutura Nasofrontalis. 1 The number of skulls examined in the present study comprise 67 males, 16 females, and 4 infantiles. The factors which govern the shape and size of the foramen magnum, and its correlative position in the cranial complex, are the same as those which govern the development of any other detail in the human organism: physiologic demand (function, adaptation) and heredity. The factors of decisive importance in our case are (1) the marvelous growth of the brain in the course of mammalian evolution, 1 Indian Notes and Monographs, vol. vn, no. 2, 1920. 7 8 SKULLS FROM and (2) in connection therewith the acquisition of the erect gait. It was shown by Bolk (1915) that the shifting or migration of the foramen magnum from a postero-occipital to an infero-occipital (basi- lar) location was due to the rapid expansion of the brain, whereas the modifications of shape and size of the foramen magnum are influenced by the erect gait which imposes increasingly changing demands on the statics and dynamics of the human head, as controlled by muscular action. Mutual interre- lations prevailing in the skeleton in general must also be considered in this connection with regard to the cranial complex, and which give rise to corre- lations between the cranial parts. So far as can be learned, a systematic investigation of such correlative factors does not appear to have been carried on. Conjectures, however, as to the mutual relation between the size of the foramen magnum and that of the entire cranium and stature are occasionally met in anthropological literature (Hrdlicka, 1906, 54; 1907, 31; 1909, 195; 1916, 31- 32; Hooton, 1920, 98, et al.). 2. PROBLEM The present investigation concerns itself with the descriptive and metrical interpretation of the foramen magnum, in the following order: (1) shape, (2) size, (3) angular conditions, and (4) correlative conditions. These latter are enhanced by classifi- catory comparison of absolute and proportional SAN MIGUEL ISLAND 9 measurements of the foramen magnum with those of the cranium as a whole. 3. SHAPE OF FORAMEN MAGNUM Owing to the general uncertainty of shape of the foramen magnum, it is rather difficult from the cranioscopic angle to describe or point out definite and unmistakable types in a given series. Its variableness may well be likened to that of the cranial form itself. While in this latter respect a number of individuals may be grouped around more primary or conservative types, a certain prevalence of shape may obtain also with regard to the foramen magnum. Such primary forms may be the elliptic and circular ones which, however, even if true to type, only rarely represent racial characters of diag- nostic value. In this respect the modifications of the primary shapes are of far greater occurrence. Hooton (1920, 112) thus distinguishes in the Madi- sonville crania between irregular, half-diamond, round, diamond, and hexagonal, while the present author in the Jesup Report (1929) recognizes round and elliptic as fundamental shapes with modifica- tions in the rhomboid, and in the oval with anteriorly or posteriorly situated bases. A racial prevalence may at times be encountered, as Haberer (1902, 87), for instance, claims of the Chinese when he says, " Das Foramen magnum ist gewohnlich gross, rhom- bisch und hat rauhe dicke Rander," or Klaatsch (1908, 127), of the Australians, stating that "the to u i^b 5.2 ^ - o X Si s > s o Coo — r-^ =3^?. J3 SAN MIGUEL ISLAND 11 diameter of the foramen shows much variation, an oval shape being the prevailing rule," but men- tioning also circular forms. In the series under discussion the author has applied the distinction of shapes as described in the preceding paragraph without, however, accounting for the anteriorly pointed oval and the rhomboid, true instances of which were not available. Regard- ing the latter it should be mentioned that the projection of the occipital condyles into the lumen of the foramen magnum frequently causes the erroneous impression of a rhomboid foramen magnum which in fact it is not. It must further- more be remembered that since true types are rather rare, their modifications are somewhat difficult to recognize, and their classification, therefore, is some- what arbitrary. Thus, elliptic and oval shapes may be very similar, while both may be quite wide and show affinity to the circular shape. Taking all these fallacies into consideration the following distinction was finally decided on: (1) ellip- tic, (2) circular, and (3) anteriorly pointed oval, which may be seen illustrated in fig. 1, a-c, after specimens in the series under discussion. Their distribution among our series is shown in Table I, where the percental participation of the different shapes is highest in the circular, slightly less in the elliptic, and still less, although at an appreciable figure of 21.7%, in the oval. The distribution among the sexes is quite interesting. Equal fre- 12 SKULLS FROM Table I. Actual and Percental Frequency of Foramen Magnum Shapes Classes Elliptic Circular Oval anteriorly pointed Total 31 37.3% 34 41.0% 18 21.7% c? 9 Inf 26 5 83.9% 16.1% 25 7 2 73.5% 20.6% 5-9% 15 3 83.3% 16.7% quencies of the elliptic and oval shapes occur in the males at 83% and in the females at 16%, while in the circular there is a relatively lesser frequency in the males and a higher one in the females. The two infantiles are also listed in the column headed circular. Irregularities around the foramen magnum, such as the various "manifestations of the occipital vertebra" (Kollmann, Bolk), 2 or others resulting from pathological or mechanical causes, do not obtain in our series. There is, however, a vari- ation in the posterior border of the foramen which deserves mention. In ontogenetic stages an inde- pendent bone, medially situated, is derived from a special ossification center in the cartilaginous matrix, Hannover 1 s (1881) membrana spinoso-occipi- talis. Normally this small bone in proper time, i.e. several years after birth, according to Gegenbaur 2 See Oetteking, Bruno, 1923. SAN MIGUEL ISLAND 13 Fig. 2. — Anlage of an ossiculum Kerckringii (Topinard), x, in a fetal human os occipitale. (After Cunningham, D. J., Textbook of Anatomy, 1923, p. 196.) 14 SKULLS FROM in the sixth to seventh year, merges with the sur- rounding occipital parts. This osseous element is the ossiculum Kerckringii (Topi?iard), or manubrium squamae occipitalis (R. Virchow), the anlage of which is shown in the fetal bone of fig. 2. In rare cases it does not merge, and this produces an emargin- ation with more or less sharp edges which then causes an elongation of the foramen. Our series does not contain such cases; a number of them instead, however, show peculiar shapings of the opisthion region which bear evidence of individu- ally variable ossification. They are easily definable as straight and more or less angularly set off against the lateral margins of the foramen magnum, or as concave or convex. In fig. 3, a-e, these variations are illustrated, a representing the normal condition of an even rounding, as in no. 314 9 of our series. A straight line, 10 mm. in length, forming mildly obtuse angles at both ends, ma}^ be noticed in b. It is an immature skull of the infant I stage, no. 267, the permanent molars not having erupted as yet. This is a particularly interesting case because of the fact that the two lateral sutures (fissures?) at each end of the straight line had not become obliterated, which corroborates Gegenbaur's statement, referred to above, of mergence of the ossiculum Kerckringii during childhood. A modification of fig. 3, b, is pictured in c, corresponding to no. 337 d 71 of our series, where the straight line that marks the medial posterior edge of the foramen magnum turns sharply flit- ®Wif l^''^»ii'-A , «\v!is t^t>T^a,K\ jmt-v- ■*"-..?■»* i?" Fig. 3. — Variation in the anomalous emargination of the posterior border of the foramen magnum. See text. Slightly reduced. SAN MIGUEL ISLAND 15 forward at right angles. These side lines again form more or less pronounced angles with the lateral margins of the foramen magnum. If the latter were connected with one another from side to side, a rectangle of only 3 mm. in depth and 10 mm. in width would result. The concave shape, as given in d of our figure, is that of no. 272 cf ; it represents a neatly shaped notch, while in e, no. 301, inf. II, where the medial portion bulges out and produces a convexity forward, this seems to be partly filled in again. Most of these shapes represent single occurrences in our series, and might be attributed directly to irregular ossification. A deficiency there of the independent osseous element hardly comes under consideration, since the notches are not deep enough to justify such an assumption. Nor on account of their scarcity can they be regarded as a racial trait, although Klaatsch (1908, 127 and plates) has repeatedly observed them in his Australian skulls, and Cameron (1923, 41c) in the Eskimo. But even in pronounced cases of absence of the ossiculum Kerckringii, such a condition must not be mistaken for knife-marks caused in maceration which at times occur somewhat regularly and which Hrdlicka (1907, 91) mentions in discussing the Gilder Mound crania of Nebraska. 16 SKULLS FROM 4. METRICAL DEFINITION OF FORAMEN MAGNUM a. Length The physiological range of the length of the foramen magnum in our series is almost identical in the sexes, extending from 29-38 mm. in the males and from 29-37 mm. in the females, while the two immatures measure 31 mm. and 33 mm. This is fairly in accord with Martin's (1928, 851) statement of a total physiological range of (25 mm.) 30 mm. to 40 mm. (43 mm.) where the parenthesized figures represent the extreme values of a Bashkir and a Tyrolese in the order of the citation. The averages amounting to 33.6 mm. in the males, 32.8 mm. in the females, and 32.0 mm. in the immatures, although quite similar, exhibit nevertheless such differences as are generally met between the sexes, as well as between the mature and immature ages, i.e. the male values exceeding the female, and the latter the immatures. If compared with other human groups, the foramen magnum length in our series is rather small, as may be seen in Table II. 3 The Japanese as well as the Australian averages exceed those of our series, and the La Chapelle-aux- Saints value of 46 mm. appears to be the highest on record. 3 Comparative data here as elsewhere are in most cases quoted from Rud. Martin, Lehrbuch der Anthropologic (1928). SAN MIGUEL ISLAND 17 Table II. Comparative Averages of the Foramen Magnum Length Classes Length of foramen magnum (averages) San Miguel Island Japanese Australians La Chapelle- aux-Saints c7" .-.'.. 9 .... Inf.... Range. 33.6 mm. (67) 32.8 mm. (16) 32.0 mm. ( 2) 29-38 mm. (85) 36.5 mm. 36.5 mm. 35.5 mm. 34.0 mm. 46 mm. b. Width The range of the foramen magnum width, like the length, comprises 10 units, extending from 24-33 mm., which at the same time represents our male range, the female extending from 24-31 mm., and that of the four infantiles from 26-28 mm. Martin's (1928, 851) general range comprises individual width values from (20 mm.) 23 mm. to 38 mm. where the parenthesized low extreme is that of a Roumanian. Our highest value of 33 mm. is thus seen to fall noticeably short of Martin's highest one. Our averages of 28.6 mm., 27.3 mm., and 27.0 mm. in the sexes and immatures, as listed in Table III, show a tendency toward smallness. The width averages manifest similar diversities to those found in the length averages. Comparison of these figures and those of the other human varieties quoted in Table II reveals similar proportions within each set of averages. It must be noted, however, that 18 SKULLS FROM the average of the foramen magnum width in the Japanese females at 26.5 mm., considering the smallness of the measurement, is markedly less than that of the Japanese males, as against the equality of their foramen magnum length measure- ments at 36.5 mm. The foramen magnum width of the La Chapelle-aux-Saints skull falls likewise considerably short of its excessive length, being thus rather comparable with the male width average of the Japanese, which in turn is slightly in excess of the width average of our own series. Table III. Comparative Averages of the Foramen Magnum Width Classes Width of foramen magnum (averages) San Miguel Island Japanese Australians La Chapelle- aux-Saints 9 .... Inf.... Range. 28.6 mm. (67) 27.3 mm. (16) 27.0 mm. (14) 24-33 mm. (87) 30.3 mm. 26.5 mm. 29.9 mm. 29.3 mm. 30 mm. c. Length- width Index The total range of the foramen magnum index is very extensive between the extreme values of 71.4 and 103.5, both being males. The female range between 72.7 and 93.1 is less extended, while the two infan tiles have indices of 81.8 and 83.9. In correspondence with the length-width differences SAN MIGUEL ISLAND 19 within and between the sexes, the male average of 84.8 slightly exceeds the female of 83.2. This condition is much more marked in the Japanese of Table IV, whose considerably smaller female average Table IV. Comparative Averages of the Foramen Magnum Index Classes Foramen magnum index San Miguel Island Japanese Australians La Chapelle- aux-Saints 9 .... Inf.... Range. 84.8 mm. (67) 83.2 mm. (16) 82.0 mm. (2) 71.4- 103.5 mm. (85) 83.4 mm. 72.6 mm. 84.9 mm. 86.1 mm. 65.2 mm. — is the result of the noticeably lesser female foramen magnum width as against the higher male width and the equality of the foramen magnum length in the Japanese sexes of Table II. The La Chapelle-aux- Saints index of 65.2 appears to be the smallest on record, owing to the excessive length and the relatively small width of this fossil's foramen magnum. 4 From Martin's (1928, 851-852) figures it may be gathered that the physiologic range of the foramen magnum index, 71-111, is very extensive and comparable somewhat to the range of the series 4 See, however, Table XI (Eskimo) and accompanying text on page 34. 20 SKULLS FROM under discussion. The average of the latter when judged by Martin's list of racial averages occupies a submedium position, thus indicating a slight ten- dency toward a bilaterally narrowing circular form. They are exceeded toward the other extreme by a number of varieties like the Bavarians, Malays, Paltacalo Indians, and others. In the majority of cases the female average falls short of the male, which speaks for a rounder foramen magnum in the latter. The reverse is shown in the Australians of Table IV. d. Module Inasmuch as there is considerable irregularity and little special significance in the ratio between the two main diameters of the foramen magnum, Hrdlicka (1916, 31-32), for comparative purposes, prefers the foramen magnum module according to the formula « • The sex differences here, of course, correspond to those of the index, i.e. there is a slight diminution in the female average. Thus, while the male average of the module amounts to 30.9, at a range from 27.0-35.0, the female average yields 29.7 at a slightly smaller range from 27.5- 33.5. The two infants fall within the general range of variation with values of 28.5 and 30.0. The fol- lowing table lists a few comparative data, where those of the other Indians are quoted from Hrdlicka (1916, 32). It will be noticed that the San Miguel Island SAN MIGUEL ISLAND 21 Table V. Comparative Averages of the Foramen Magnum Module Classes Foramen magnum module San Miguel Island Arkansas Munsee La Chapelle- aux-Saints &.. .. 9 .... Inf.... Range. 30.9 mm. (67) 29.7 mm. (16) 29.3 mm. (2) 27.0-35.0 mm. 33.0 mm. (22) 31.0 mm. (16) 35.0 mm. (7) 32.0 mm. (8) 31.0- 38.0 mm. (15) 38.0 mm. averages are exceeded by the Arkansas and Munsee, and these again by the Chapelle-aux-Saints module of 38.0 mm. A module of the same height occurs in the Munsee range as listed in Table V. e. Angular Relation to Ear-eye Plane The angle is formed by the basion-opisthion line representing the foramen magnum plane, and the ear-eye plane, or better, its parallel through the basion. Using Broca's terminology, the angle is positive ( + ), if situated above that parallel, and negative ( — ), if situated below it. Both angles open posteriorly. In fig. 4 these conditions are schematically illustrated. The positive angle, con- sidered from a morphologic viewpoint, is a primitive condition found in Simiidae where it ranges from 22 SKULLS FROM + 55° (Cebus) to + 19° (Gorilla). More advanced conditions obtain in the extinct and recent varieties of Homo, while in the Hominidse as shown in the La Chapelle-aux-Saints skull, the more primitive angle of + 7° occurs. However, instances of positive angles occur also in almost any human Fig. 4. — -Schematic representation of the deviations of the foramen magnum plane from a parallel of the ear-eye plane (e-e') passing through the basion. + angle above, — angle below, the parallel; ba, basion; o, opisthion. variety, while the general behavior here is that of an advanced morphologic state as signified by the preponderance of the negative angle. In Europeans Fr. Sarasin (1916-1922, 195) states an average of — 12°, while in New Caledonians the males yielded an average of — 3°, the females of — 6.7°. Com- pared with these findings the San Miguel Island averages and those of the western Eskimo of Table VI range somewhat higher, falling in fact between the more primitive New Caledonians and the more advanced Europeans. One feature, however, is common, or at least preponderant, in all the vari- eties, i.e. the greater minus angle in the female SAN MIGUEL ISLAND 23 skulls which probably is due to the sex differences in general cranial structure. In the present series only one instance of a positive angle has been met, the general range beginning at + 3° and extending to — 22°. The averages yield angles of — 9.4° for the males and — 13.2° for the females, and from whose range of — 5° to — 22° a higher average might have been anticipated. The two immatures have angles of — 7° and - 11°. Table VI. Comparative Averages of the Foramen Magnum Angle Classes Foramen magnum angle San Miguel Island Eskimo 5 Alaska and Siberia Chinook (deformed) cf .... 9 .... Inf.... Range. - 9.4° (67) - 13.2° (14) - 9.0° (2) + 3° to - 22° (83) - 7.1° (32) - 9.8° (12) + 2° to - 19° (44) + 0.6° (56) - 0.5° (24) + 14° to - 15° (80) It is of interest in this connection to compare the status of the foramen magnum angle in a deformed 5 The data of the last two columns of Table VI are from the present author's report, now in print, on the North Pacific crania of the Jesup Expedition. Regarding the Chinook findings, see also Oetteking, Bruno (1924), Dec- lination of the Pars Basilaris in Normal and Artificially Deformed Skulls, Ind. Notes Monogr., misc. 27. 24 SKULLS FROM group. Among the skulls mentioned in footnote 5, there is a series of 56 male, 24 female, 5 infantile, and 4 juvenile Chinook skulls. This tribe, as is known, practised excessive anteroposterior skull deformation which, besides causing considerable distortion in the configuration of the skull parts, brought about changes at the base of the skull. The total range of variation comprises angles from + 14° to — 15°, and it is quite significant that the infantile and juvenile ranges contain only plus values + 7° to + 4° in the former, and + 8° to 0° in the latter, while the male and female ranges extending into the minus region amount to + 14° to — 15° in the former, and + 7° to — 10° in the latter. The averages accordingly aggregate + 0.6° in the males, — 0.5° in the females, + 5.2° in the in- fancies, and + 3.0° in the juveniles. 5. CORRELATIONS The morphological interpretation of so complex a unit as the human skull must needs rely, to its greater extent, on quantitative determinations. Diameters and their proportional relations expressed in percental indices, however, do not fully solve the problem: they disclose only insufficiently the inter- dependence of parts in the configurative sense. Thus, while quantitative determination must be the basis of all differential treatment, the inter- pretation of form may be greatly aided through the SAN MIGUEL ISLAND 25 examination of the correlations of parts that form the complex. Although different methods were applicable and suitable to our specific use, the counterposition of metrical findings was preferred, the problem thus treating of the correlation between the dimensions, shape, angular position of the foramen magnum, and certain cranial dimensions and proportions. In the order of their importance the investigation of mutual relation was carried on, first, between absolute measurements of the foramen magnum and the cranium; secondly, between their proportional evaluations; thirdly, between the foramen magnum angle, and absolute foramen magnum and cranial measurements, and the proportional evaluations of the latter. a. Mutual Relation between Absolute Cranial and Foramen Magnum Measurements a. cranial length and foramen magnum LENGTH The averages of cranial length in the present series amount to 177.0 mm. and 170.1 mm. in the sexes, and 160.7 mm. in the infantiles. They show the usual sex difference, ranging rather low when com- pared to other racial averages given by Martin (1928, 765) with male and female ranges of 174 mm. (Bashkirs) to 187 mm. (Scotch), and 165 mm. 26 SKULLS FROM 8 3 8 „ -I 8 8* 3 > w < g S B E S E 3 c S 6 E S E s bo ,—v^-^,— „ ^-s^~ ' B s S3 oo j>- ro -xH C 1 1 - T1 NO CD On On t— co co s cn cn co co to v — 'v_^v ' V — --s o ooqc rH io fa co esi es CO CO CO CD CO CO J>vOt> CN i- o NO i— i CO T- .£5 bfl a> 6 S E S £ J S S E S E 3 CO lO nC r cn o r s "j3 On t— vc ) ONi> • B aj HWr 1—1 1— u 1 1 I 00 -*f ir ! 1 > t- NC § NO no ir > NO NC c^ Hrtr- i— 1 i— ^-^ — 'v_ ^ * — '-^_ O t-H I- On t> l^OC 1-h c- r^t— nc oo j> Hrtr i—i i— CO CD CO 00 NO VC co cv nj NO i— 1 CO T- O CO +-> C a -a in to a J2 ^^ k 3 "C 'w • • <*. "8 ' CjJ Cfl a> u^O) i "a; Oh o TO § .6 J, u c 13 nj CO oj W W J ■Sg cu TO Ui CD o c o cu +J ■+-• _!_) ° - 1 - c _, +■> .3 CU cu o TO .2 to TO CD m 0) O CD +J 4-> O nj O <-4— I 5 s s C C n3 o"o3^ _ JCJ C NO +-> °^ r-. u -0 3 c +-" CO Cfl in c c 3 o cn^ O §|e2| U i ° 4) C 3 0) d CO cu cu B S SAN MIGUEL ISLAND 27 (Telengets) to 179 mm. (Scotch) respectively. In Table VII the length averages of the cranium and the foramen magnum of our own series are con- trasted with those of another group and a neander- taloid specimen. From this tabulation it appears that an increasing cranial length as represented by the sex averages is associated with an increasing foramen magnum length, a fact which is evident in our own series as well as in the Eskimo and the human fossil listed there. As to the differential correlation between the two diameters under investigation within our series, the cranial length as shown in Table VIII was divided into three classes, containing the individual values from 164-169 mm., 170-179 mm., and 180-189 mm., and the foramen magnum length computed for each of these classes. The infantiles, on account of their small number, have not been listed in the tables, but are mentioned in each case in the discussion. In the males, the foramen magnum length for the division of smallest cranial length with 34.8 mm. slightly exceeds that for the medium class with an average of 33.0 mm., only to increase again to 34.7 mm. with the class of greatest cranial length. It is quite possible that the disparity of successive in- crease in the male averages is due to the small number of cases in the class of lowest cranial length. The fact, however, that high individual values occur there cannot be disputed. In the females whose 28 SKULLS FROM B B ►si B B CCj no t— 8 Pi co co <« 1 ^ Os co CN CO g 3 8 o © CM 8 S < oJ co 54 3 CI M ecJ co co « s CO CO CO cd nO O 1 01 s CJ o .^ ►** "3 g o S 6 6 is OJ BBB s^ C Cti t^ oo t^ ° s c CU tf co co co 1 1 1 *> e h-1 CNC>H ^S IT) CO CN CO s ->* if ■b CO s s s ►O !3 u £ B B 1^ > CX)ON < ^" CO TjH •<~> co co CO "§ >~<> « CO *^ &> ^ CO ■^ '-< CM a cd U ^ CN »— 1 1— 1 \—{ > ,-C ^O B B B w n < S fi ») BBB On On On NO J>~ 00 T— 1 1— i •«— 1 H 1 1 1 tH o o no t^ oo T— 1 1— 1 T— 1 averages comprise only the first two classes, the smaller cranial length combines itself with the lower average of the foramen magnum length, while the me- dium class shows an increase over the two. Two infantile skulls with foramen magnum lengths of 31 mm. and 33 mm., as specified in Table VII, have smaller cranial lengths of 161 mm. and 166 mm., which establishes the expected correlation be- tween the two mea- surements. Some sig- nificance, however, seems to attach to the ranges of the foramen magnum length classes as correlated with those of the cranial length. Thus, while the female ranges show an even increase, the male ranges are per- SAN MIGUEL ISLAND 29 fectly irregular, which may be due in part to the small number of cases in the class of shortest cranial lengths, as pointed out above. |8. CRANIAL BREADTH AND FORAMEN MAGNUM WIDTH The two breadth measurements, the cranial and that of the foramen magnum, have been treated in the same way as the respective lengths in the pre- ceding section. In Table IX both measurements are contrasted. On the basis of Martin's (1928, 766) list where the male averages for the cranial breadth range from 128 mm. (Vedda) to 153 mm. (Buriats), and the female from 124 mm. (Vedda, Paltacalo Indians) to 145 mm. (Swiss [Wallis], Telengets), showing the usual sex differences, the San Miguel averages as recorded in Table IX must be characterized as rather submediun. There are also among the individual values, if compared with Martin's physical range of from 101-173 mm., only few above medium condi- tions. The La Chapelle-aux-Saints skull, quite in proportion with its inordinate length, is seen to exceed in cranial breadth any of the San Miguel and Eskimo specimens, while the latter exceed the San Miguel skulls by only a trifle. As regards the foramen magnum width of the La Chapelle-aux- Saints skull, this falls, with 30 mm., about half-way between the extreme values of the Eskimo male range, a relation which will be of significance in the 30 SKULLS FROM r-s: s 6 6 6 6 6 t3 5 6 6 6 6 6 t^ 4 M ^ S5 CO H 00 CO CN fOCOCN CO CO § 1 1 1 ** ^ NO 1 1 6 oq cm (N CN CN - 6 S £ ' v. — xv . vq co o co MD o O 00 t^t^ CNCNCN On OO CN CN co 8 50 co <3 CO t^ NO ^f 1 CO «— 1 O NO H CO •«— i fen 6 6 6 6 6 6 6 6 6 6 -u ,-^,~^<— X ^^^~ 53 OJ hOOO O CN iO tJh co lO ^ *" 50 1 I 1 1—1 T— 1 I 1 CQ «xo "c3 O OOn oo 6 6 II ? co co CN co CO a 50 '3 T— 1 1— 1 T— 1 T— 1 T— 1 l>rOt> O *H NO lO ON U-j CN © ^o T— 1 ^-> £ CO co co ^ co 5o T— 1 T— 1 T— 1 tH t— 1 co 4J CO 00 NO NO CO CN 50 W 50 50 50 O u NO ■<— l CO t-H fC> s o CO +-> g 50 *^ cd *U w co J2 i 3 "Jh 1X1 'CO • " I*- CD 3 c? '53 m 6j0 Oh pa g o 6 -G oq os s < Oi> s CN Cs| a CO a (LI c CO as oo oo J +-i s b s s* o ^3 0) M a e s s •3 (3 rOCNfOrn s P4 ro fj <~o CO 1 1 1 1 II ^ t}h u-> 00 ■b CNtNCNCN cu M c8 1-C fi B B S BBSS CU > lOvOVOCX) < 00° 00 00 00 CNCNCNtN CO CL> Oi ^LOfOlO r-lCStN S 6 B B 08:5,2 BBSS ■3*dS lO O lO t-H J3 OJ CO CO ^ *vh to o|| T— 1 T— 1 T— 1 T— 1 1 1 1 1 o OOrnvo rOfO^TJH 1— 1 T— 1 T— 1 TH 32 SKULLS FROM 28 mm. and fractions, and it is only by the latter and by the ranges of the four classes that an in- crease, however slight, may be realized. Four infan- cies with cranial breadths between 129-138 mm. have also small foramen magnum widths of an increasing order from 26-28 mm. b. Mutual Relation between Propor- tional Evaluations a. cranial length-breadth index and foramen magnum index The averages of the cranial length-breadth index show the typical increase in the order males, females and infantiles, and, with the exception of the latter who are brachycranial, fall into the mesocranial class. This is also true of the Eskimo included in Table XL In the San Miguel skulls the averages of the foramen magnum index when compared with those of the cranium show a gradual decrease as against the increasing cranial averages. These conditions, however, are reversed in the Eskimo in such a way that with the increase of sex averages the foramen magnum index likewise increases. This being also the case with the Australians of Table IV, it may be assumed that the proportions between the averages of the foramen magnum index in the various groups of mankind vary as to sex. The SAN MIGUEL ISLAND S3 E 3 t s b s s tJD S B rt io* ^ ^ , — s , — s £ co' -1 <* CN r^ e O r ^ t*3 1-H i-H (LI £ t-h On 00 1 1 On On 1 1 CN 03 ^ t- ^ oo 00 CD lO Ih 00 • CN • O • *>■ * "^ ~ NO O .1—1 . CN .i-H • CN • O X fa "*t^r^N- \Q CN CN i-H T3 rt no '—i CO t— 1 '1 U s e s 6 S CL> see a b >H ,Q On co co sr- co ^3 -i-> rt CO co u"> i-H CO 'S u u 1.9-8 7.0-8 0.1-8 1.0-8 4.4-8 q t^ t— 00 j>- t^- LO v — " •> — ' *• ' v ' ~^S t^ Tt< CN CO q q 00 On CN t-^ On :>- j>- oo i~- t-~ en CO f~~ NO NO CO CN oJ u NO rH co ■<— i en +-> g nj T3 CO CO 1 3 c ■H 11) n guel Is 9 . Inf. g. i a • ^-t o 0J § B c 13 a CC R3 CO w J 34 SKULLS FROM B S £ S 8 D Qi M t— 1 1— 1 g vd co 13 f* 00 On 1 1 « r^- C\ CN "*" «o t-~ 00 -S» o ***i -s 8 6 6 Q 9 Ih a a > ^f to ^.■2 <3D '"•H X 3 ?3 Co, sag 8 a 0) 10 co t-h . .*>■ ^ o p] • • co fe 1 1 1 ^3 oqq4 SO &} - *b be ca ass *8 8^ ass CU > 00 00 tX) < On ^'10 !>• cX) CX) £> 5X0 CO cu CO CO CO 1— 1 1— 1 X H m < .d s s s r c L CI a a a ON On CS "=f Cs t^ t- t— 00 1 1 1 ON O O co c r* 1 1 1 _ x CO to O On"o- fOCNtN © o co pr co \OtN - 03 -t-> C a3 TD CO C i ri X 3 CO "C X a 6 6 a s iO o G co co° P* co co 1 | i i IO IO t~^ 0\ o CN CN M 6 B 6 B > tJJO V < On h 3 -a o co co S to E CO CO CO 1 rt i-i 1 3 U c e a a a c (LI a a) BBS »0 *-~ rf - 5 00 IO tH co ^i iO Eskimo of the same table yield higher cran- ial modules to which the foramen magnum modules are in propor- tion. The highest values of our table, of which only the for- amen magnum module of 38.0 is doubled in the Eskimo female range, are those of the La Chapelle-aux-Saints fossil whose cranial measurements, at least the length and breadth, were found to exceed by far the averages and ranges of the other groups of our tables, 8 this holding true also of the foramen mag- num length. The high foramen magnum mod- ule of the La Chapelle- aux-Saints skull is ac- 8 For the cranial height Boule gives 131 mm., a value falling well within the San Miguel and Es- kimo series. SAN MIGUEL ISLAND 37 counted for by the length rather than by the for- amen magnum width. In the correlation scheme of Table XIV it is made manifest that in the males as well as in the females of the San Miguel Island series the averages of the foramen magnum modules increase proportionately in the successive classes of the cranial module. c. Mutual Relation between the Foramen Magnum Angle and Absolute and Pro- portional Foramen Magnum and Cranial Evaluations a. angle and length of the foramen MAGNUM From Table VI it was gathered that the sex aver- ages for the foramen magnum angle differed in such a way that the female average yielded the higher figure, i.e. higher minus value, thus representing a more advanced morphologic condition. This held true not only for the San Miguel Island series, but also for the Eskimo of the same table, and it may be inferred that this is quite probably the general behavior in the human groups. 9 9 From the physeotypical viewpoint one may be led to assume that the tendency toward greater female short - headedness in the comparative sense as a response probably to the less extensive backward and the more intensive lateral and downward expansion of the brain (Bolk, 1915), influences the orientation of the foramen magnum plane in such a way as to force the opisthion region downward, as against the more conservative basion region, which then would account for the greater minus angle of the foramen magnum plane. 38 SKULLS FROM -si ^ 1 -si .. ^ a > X < CM CM t- On C 7^ > 1 1 *7 • I I o o o c > > V +-> +-> . Pi < CM Ti tl o o o O o > '"I cc . + On I o i i t a 1 "J 1 1 1 1 s to a M s S3 to J>~ ■** cm CN CS o VO *-H CO i- a; s cS J-i s '£l B E O fa gg£ S E J2 I ir ^ f)POfC co CO CO to NOCN CM -- 03 \0 -»-H ro t- O tn +-> C a3 TD in c i a3 X co In -1 ,o - z ,a 3 0) CO g "a3 • »-H O ri ^ B J3 c 'JZ u ctf cc 03 C/3 w 1 J SAN MIGUEL ISLAND 39 The combination in Table XV of the sex averages of the foramen magnum length and angle demonstrates, from the purely met- rical viewpoint, that the smaller female average of 32.8 mm. is corre- lated with the larger average of — 13.2°, as against the male aver- ages of 33.6 mm. and — 9.4°. Analogous proportions, but with comparatively higher length averages and smaller angle averages, obtain in the Eskimo, while an exaggeration of these proportions is shown by the La Cha- pelle-aux-Saints values. The general trend of these proportional con- ditions may be seen corroborated in Table XVI, in which in the males as well as in the females the averages o o o ~ CN On tJh § tNHH 3 co 1 1 1 fed a a! 1 1 1 o o o 1 rt o o o 8 ^ 1 1 ^ Q 1 ' ' v o <3 QJ O O ft, M cd l-H qooq od oi © ■JjS > 1— 1 T-l T-t > V < 1 1 1 M ^ a a W CO § s B w cd U co 00 co i3 3 a a M Cd S ^ 3 a CO s cd u o M o o O H O CN CM 00 1 1 1 'I 8 fe a o o o S Q cd -t-> -M +J ^&Q P4 o o o "**S ■^ CO CO £•* 1 1 1 ■« 50 "b o o o t» 0, co iO 00 OS SI cd i-h" On vd -. 7-1 1 1 -O co > 1 ' ' § 3 1 — ^ 0} ^ K cu en ^Ot>-rt< V o o cd T^ ,— 1 U 1— 1 > X W n < a a t? B B B 0) <-; c- HI o 2^i5 d, a ^o b a b © lO OO co <^> ^ 1 1 1 On '-i ^O H rsi co ro 40 SKULLS FROM -Si w a > X w m < ^^ ,—>.•— t-H CN Ov c CN CN s~ N HCV 1 1 ,— l 1 1 1 t- 1 1 o o 1 o c +-> +-> +-> +- JH miot^ CN ^ + 1 1 ii < ^ v - /v - ,, o o o o "* °i c o tH 0C + Os'ro© J>-' O s l 7 ! 1 1 3 co £ cu m *~» ^ CN CN CN cti u VO tH co i- s 0) g G3 10 '"N^ <• , ^s~ O X i i • CN ^ ,-1 T- O O- 1 1 a) -vt< t~~ OC 00 co a r- 1 CN t— CN C 1—1 t^ir- OC vO t^ CN v-^v^^_ W-_ lO oo cn C t^ ^ vO rjn ffj cs 00* c 00 00 OC t~~ OC co CD CO t-- o cn CN t- ai vO •■-< co r- O CO +-> G <& T3 m 3 J5 i X! 3 "I a u J J ojO 1/5 K-" cj3 13 a O aj § s U C 13 a to cS m W J of the foramen magnum angle decrease with the increasing classification of the fora- men magnum length. jS. ANGLE AND INDEX OF THE FORAMEN MAGNUM The aver- ages of the for- amen magnum index, as spec- ified in Table XVII, decreas- ing in the San Miguel Island series from 84.8 to 83.2 in the sexes, yield in- creasing aver- ages of the for- amen magnum angle of - 9.4° and -13.2° SAN MIGUEL ISLAND 41 respectively; while the infantiles, num- bering only two, with an index aver- age below those of the sexes, come only to — 9.0°, a condi- tion doubtless due to their undeveloped physical state. The different order of in- dices in the Eskimo, i.e. 78.7 in the males, increasing to 80.4 in the females, as pre- viously pointed out (page 32), shows nevertheless increas- ing averages of the angle, — 7.1° and — 9.8°, indicating that the order of sex averages of the fora- men magnum angle, i.e. increasing from male to female, is rather a stable one and, at least so far as the two human varieties of Table g cn On s ■<— i 1— 1 8 1 1 tao M 1 1 1 O O 4-> +J O O IS IO 00 g 1 1 3 o fen u 000 50 M l-H co # "* O 00 ^' CN -*<* CU > CO g^ 3 a 3 cu CO 03 •^Oirt a be s O **3 ^S 000 *5 ^ a B a u O O y-t y— 1 CN CN) J5 a 0) M 1 1 1 OOO +-> +J +-> ^ 1 A OOO qo°0 O co co + 1 ■b <50 •<•?> cu OOO M fOJ>. O »0 r>? a3 - f* On CN 8 <3 CU > X v H * 11-s ^^co* w £$.£ OOO pq Zs 00 On t-( I 1 1 -^ CO CN H ■<— 1 T— 1 T— | t- 00 On 42 SKULLS FROM XVII are concerned, is independent of the behavior of the foramen magnum index averages of the sexes. While this is probably the general behavior in any series of human skulls, the distinctly increasing order of the angle averages in both sexes for the increasing classes of the foramen magnum index, as shown in Table XVIII, is quite interesting. y. FORAMEN MAGNUM ANGLE AND CRANIAL LENGTH It is shown in Table XIX that the averages for the cranial length, decreasing naturally in the sexes and immatures, are correlated with increasing aver- ages of the foramen magnum angle so far as the sexes are concerned. 10 The angle of the immatures, on the other hand, decreases again and with 9.0° falls even slightly below the average of the males. As previously mentioned, this latter condition must be attributed to the undeveloped state of the infantile cranium. The Eskimo of the same table present analogous successive differences in the average expressions. The slightly higher averages of the cranial length are correlated with somewhat lower averages of the foramen magnum angle. This proportion is carried to excess in the La Chapelle-aux-Saints skull, whose inordinate length of 208 mm. combines itself with a 10 See footnote 9. SAN MIGUEL ISLAND 43 8 ^ s a >«. 50 ^ ,© k, to 50 50 *» -s: s 50 S? s 50 CM 50 v^ a X I— I X w m "3j CN CN -— ^ *— i cn 1 rt 1 1 ^"" 1 i i oJ 1 1 ,- < I I s o o 1 O C ) 3 +-> -M +-> -t- > fO lO J> CN tJ H 03 S + iJ + I • ° C CL> t^ o o o o o tH OC > + 03 On ro O \ J>^ O )H i i o | | fe i 1 CO CD j>~ -^ o CN CN 03 vO '—i CO i- o 1 S S £ 6 E S 6 E e e x: / — ^ — ^^~ -* , S^~ M ro iO NC CN O d On t- nc On 1> i> 1 1 1 i— i i— 15 1 00 ^ u- t~- NC OOW NO NC 3 T— 1 *— 1 T— y—i i— ^-•s • %*_ X N — • s^ O O t— i t~- On CN § t^ o c t— i rr CN !>• t^ NC CO I> T— 1 T— 1 T— T— 1 T- CO 1) CO 00 NO MT CO CN 03 \0 *— i CO T- u cc -M C «J T3 CO C 1 X! 3 CO en • •«*. +£ • ai .a "C oj "bo JH Cfi 3 "a) coo * ** Q- .^H o 03 S J JH U c 13 ct3 en oj co W J 44 SKULLS FROM Si 8 lis | "So i^ a X w l-J M < O CS On CN r-t 0) 1 1 M 1 1 c oJ o o rt +-> +-> o o o 1 1 a; O bfl c3 m > vq ro tH cn 1—1 T— 1 d> < 1 1 "5o CJ rt co E 1) CO NO 00 | U c$ £ o o o c 00 i-< o B HtNM i i i CD M 1 1 1 O 0) o o o f*i +-> +J +-> o o o lOfOH 1 + 1 'b 0) O o M fOCMO 0$ O On 00 CD •»— i i i > I'S fen 8 CM *j 8 « t-i 8-8 •^> ^3 3 x x w PQ < ^^_^ s^^- cu ^— 1 CN ON C "m CN CN -— ■v rHCN e 1 1 *■" 1 1 a 1 1 T- 1 1 £ O O 1 O C > 3 +-> +-> +-> +- a M fO»ON s + 1 1 + 1 • a X ~-' N ~' V ~- y *^s--— t^ CD OOO O O £ >*tNO HOO ~T rt On^O^ x>^ O 1 "^ 1 1 1 ta ' 1 ' 1 1 co CO 1>- ^ CN CN C-- O NO rH CO r- 1 X •0 On CO C" !>. C<- a roro"" > T-I r<- 1—1 00 GO OC ) 00 OC u 1 1 1 1 | pa 0\0-- ! °. C 1 rHt>iC > T-5 Tj j>- r- oc ) t^J> "3 w-~_ ' ^^^~ 10 "3 u Tfj cn c > OC *>: 00 On CN t^ U t^i>- OC ) J>.J> CO CD CO t^ VO vc CO cs NO i-H CO ,- tn +-> C C3 -v in c 3 CO "cfl M- Id n3 cu - r b 0f ^ g. JU cd a O Cj S B U C 13 ctS cn a (75 w J 46 SKULLS FROM so 8:^ 8 8 *§ SO ^3 ^^ £^ ^§ V. .*° I— i ^s kj bo n s w n < o o O CN i— ( CN 4) 1 W c o o OJ +-> +J * o lO ro o '7 0) o o M O CN t-I J^ > < i— I *— 1 OJ 1 1 M 03 co 3 (U 1 Os iO C u M B o o fl -* -^H O a; rHtNCN S 1 1 1 a 3 1 1 1 O c o o o fe a! ■!-> +-> +J o o o CN ro t-h "o 1 + 1 0) o o o M 03 OOT-lfO !>■' On © a; 1 l y— i > < 1 CO (L) CO *oatN 03 ro cn u «,--> nial inde sified OS ON_ CN 2*2 T^ Os Tf UWjS t^- lr^ 00 J^ 1 Os © © r-ilO O t^.i>- CO males appear to be slightly less meso- cranial. The comparatively low index of 75.0 of the La Chapelle-aux- Saints cranium has also the least special- ized angle of -f- 7°, the morphologic sig- nificance of which, however, lies with the difference in species. The metrical corre- lations in the sexes are repeated by the clas- sified index-angle cor- relations in each of them. It is shown in Table XXII that with the increasing length- breadth index classes, the sizes of the fora- men magnum angles also steadily increase. The more advanced conditions in this re- spect are shown in the female cranium, not only by higher SAN MIGUEL ISLAND 47 angle averages for the same classes of the cranial length-breadth index, but also by the fact that in the lowest index class there is no female repre- sentative, this being, however, fundamentally a question of cranial length-breadth proportion in the females of our series. 11 6. CONCLUSION AND SUMMARY The preceding study concerns itself with the morphologic, metric, and correlative conditions of the foramen magnum in the San Miguel Island series of crania in the collection of the Museum of the American Indian, Heye Foundation. Regarding its shape, the foramen magnum with most cranial series shares a certain indefiniteness which in the present series is signified by a slight predominance of the circular. The frequency of this shape, how- ever, is approached by that of the elliptic, and, to a lesser degree, by the anteriorly pointed oval. The latter two when combined exceed the frequency of the former. Anomalous formations around the foramen magnum such as the "manifestations of the occipital vertebra" {Kollmann) do not occur. In a number of cases notch-like dilatations were ob- served, too unpronounced, however, to assume a missing ossiculum Kerckringii, but due nevertheless to irregular ossification (fig. 3, b-c). 11 In respect to this see footnote 9. 48 SKULLS FROM The absolute length and width dimensions of the foramen magnum show in their average conditions the typical differences, more or less stressed, be- tween the sexes and between these, i.e. the matures and the immatures, in a diminishing order according to the differences in physical size. The average ex- pressions for the length and width are both markedly low and rise in comparison only slightly above the lowest values of a racial range of variation. The limited dimensions of the foramen magnum are likewise evidenced by its module which in consider- ation of the nature of the measurements ranges on the average distinctly below the tribal varieties of Table V. The length-width index as a proportional expres- sion of the two principal dimensions of the foramen magnum corroborates the results of the visual examination. Its average signifies a somewhat rounded foramen with a slight tendency to narrow from side to side, which is more noticeable in the females, and in the latter appears to be the rather general occurrence in the human varieties. Excep- tions to this statement occur, while on the other hand the generally close approximation of the sex averages may show stronger divergences, as, for instance, in the Japanese and Paltacalo Indians with male and female averages of 83.4 and 72.6, and 88.0 and 79.5 respectively. Investigation of the angular position of the fora- men magnum plane in the cranial complex in relation SAN MIGUEL ISLAND 49 to the general plane of orientation, i.e. the ear-eye plane, reveals several interesting results. The aver- age angularity is marked by unmistakable differences in the human varieties. The San Miguel averages, for instance, when compared with Fr. Sarasin's European average of — 12°, almost equal it, while the Eskimo fall distinctly lower, as do in turn the New Caledonians and the human fossil. If this signifies racial characteristics, these are still further emphasized by the marked sex differences in each case which yield the higher averages to the females. The cause for this remarkable distinction, as sug- gested in footnote 9, must be attributed quite probably to sex differences of physical growth and type which primarily govern all and every physical formation and which, in this specific case of the brain, influence commensurably the form of the skull; this may, in consequence, result in the increased declination of the foramen magnum plane. Quanti- tatively expressible, this distinction stands out quite clearly, while physiologically no satisfactory expla- nation can yet be offered. The systematic investigation of the mutual or correlative relations between certain cranial and foramen magnum measurements and proportions results in a number of interesting observations. The investigation was carried on in such a way that the sex averages of a special measurement, as well as the averages derived from its suitably divided range of variation, were placed in contrast to the sex 50 SKULLSFROM averages of another measurement to which they were to be compared, and to those averages of the latter as checked with the divisions or classes of the first measurement. This is shown in the subjoined table of correlations. Definite correlations, holding good for both the sex and class averages, could be established between the principal dimensions of both the cranium and the foramen magnum to the extent that the increas- ing cranial length and breadth were correlated with increasing length and width of the foramen magnum and naturally for the modules implicating the addi- tional cranial height measurement in the cranial module. The same gradual increase was observed in the divisional correlations as based on the classes of the cranial length-breadth index, but not with regard to the sex averages which, increasing in the order male-female, encountered decreasing foramen magnum sex averages in the San Miguel Island skulls, while, for instance, in the Western Eskimo and Australians, the first, i.e. increasing order, was retained. This condition is reencountered in the combination with the foramen magnum angle where the foramen magnum index is used as a base. The conflicting order of graduation of sex averages in the latter, i.e. either increasing or decreasing in the human varieties, as pointed out in the preceding sentence, is correlated, however, under both these conditions with only increasing averages of the angle. The increasing class averages of the foramen magnum Table of Mutual Relations {Correlations) between Average Foramen Magnum and Cranial Metrical Quantities in the Sexes and the Graded Divisions of Ranges of Variation of Basic Measurements, in Descriptive Terms. The Metrical Accounts may be Looked for in the Various Tables. Classification Correlated metrical quantities Cranial length Foramen magnum length Sexes Increasing Increasing Classes Increasing Increasing Cranial breadth Foramen magnum width Sexes Increasing Increasing Classes Increasing (only slightly) Increasing Cranial L-Br index Foramen magnum index Sexes Increasing f Decreasing (San Miguel Is.) Classes Increasing \ Increasing (Western Eskimo, [ Australians) Increasing Cranial module Foramen magnum module Sexes Increasing Increasing Classes Increasing Increasing Foramen magnum length Foramen magnum angle Sexes Decreasing Increasing Classes Increasing Decreasing Foramen magnum index Foramen magnum angle Sexes Decreasing 1 .,. , .. , Increasing ? j see third item above Increasing Classes Increasing Increasing Cranial length Foramen magnum angle Sexes Decreasing Increasing Classes Increasing Decreasing Cranial L-Br index Foramen magnum angle Sexes Increasing Increasing Classes Increasing Increasing SAN MIGUEL ISLAND 51 index, on the other hand, are prompted by increasing averages of the angle. Identical results were ob- served in the combinations of the cranial and foramen magnum lengths with the foramen magnum angle in such a way that with the decreasing length averages in the sexes in the order male-female, the averages of the angle increased while the increasing class averages were correlated with decreasing averages of the angle. There is another phenomenon implicated in this, namely, the higher foramen magnum angle in the female skull, i.e. its greater minus angle (page 23, Table VI) as correlated with the smaller absolute cranial and foramen magnum lengths, and vice versa. The proportions, however, between the cranial length-breadth index and the foramen magnum angle show an even progression in the sexes as well as in the classes. i The infantile values, although recorded in the tables, naturally have no significance from the viewpoint of systematic comparison. Of greater import are the findings upon the human fossil (La Chapelle-aux-Saints) which with its larger dimensions combines morphologically inferior traits of the foramen magnum, particularly with regard to the excessive length of the latter and to its markedly low foramen magnum angle (+ 7°) of phylogenetic significance. The investigations carried on in the study of the foramen magnum of the San Miguel Island skulls give rise to the following summarization: 52 SKULLS FROM 1. The shape of the foramen magnum is roundish. 2. Its size is submedium to small, with the typical sex difference according to physical size. 3. The somewhat smaller average of the length- width index indicates in the females a slightly narrower foramen magnum as compared with that of the males. This condition is shown to vary in the human varieties. 4. The greater degree of minus declination of the foramen magnum plane in the female crania, also in other human groups, signifies a more advanced morphologic condition. Size and type differences in the brain, regarding which no studies have as yet been made, are doubtless causative for the varying conditions of cranial morphology in the sexes. 5. The study of mutual relations between different measurements reveals the following correlations: a. Simultaneous increase in absolute cranial and foramen magnum measurements. b. Varying behavior between the sex averages of the cranial L-Br index and the foramen magnum index, i.e. increasing-decreasing in the San Miguel Island skulls, but simultan- eously increasing in a number of other human varieties. A simultaneous increase, however, is the distinguishing mark of the class cor- relation between the indices in question. c. Foramen magnum and cranial lengths are cor- related with the foramen magnum angle in such a way that with the decrease in the sex SAN MIGUEL ISLAND 53 averages of the former, increasing averages of the angle are observed, while in corroboration the increasing averages of the subdivided ranges of the former are prompted by the decreasing averages of angularity. d. The foramen magnum index, varying in regard to the graduation of sex averages in various human groups, is correlated with invariably increasing sex averages of the angle; but simultaneous increase of averages obtains in the classified averages of both categories. e. Simultaneous increase of sex as well as class averages was observed between the cranial L-Br index and the foramen magnum angle. 12 LITERATURE Bolk, Louis 1915 Uber Lagerung, Verschiebung und Neigung des Foramen magnum am Schadel der Primaten. Ztschr. Morph. Anthr., v. xvn, pp. 688-692. Cameron, John 1923 Osteology of the Western and Central Eskimos. Rep. Canadian Arct. Exped., 1913-18, v. xii, pt. c. Hannover, Adolphus 1881 Le cartilage primordial et son ossification dans le crane humain avant la naissance. (Orig- inal Danish, 1879-80.) 12 Experiment with a number of other more or less closely related measurements of the cranium to those of the foramen magnum not recorded here, revealed similarly identical correlations. Higher mathematical differential methods (coefficient of correlation) were not resorted to on account of the relatively small series of specimens under investigation. 54 SAN MIGUEL ISLAND Hooton, Earnest A. 1920 Indian village site and cemetery near Madi- sonville, Ohio. Pap. Peabody Mus. Amer. Archaeol. Ethnol. Harvard Univ., v. viii, no. 1, pp. 83-137. Hrdlicka, Ales 1906 Contribution to the physical anthropology of California. Univ. Cat. Publ. Amer. Archaeol. Ethnol., v. iv, no. 2, pp. 49-64. 1907 Skeletal remains suggesting or attributed to early man in North America. Bull. 33 Bur. Amer. Ethnol., Washington. 1909 Report on an additional collection of skeletal remains from Arkansas and Louisiana, Jour. Acad. Nat. Sci. Philadelphia, v. xiv, pp. 173-249. 1916 Physical anthropology of the Lenape or Dela- wares, and of the eastern Indians in general. Bull. 62 Bur. Am. Ethnol., Washington. (Reprinted as Contributions Mus. Amer. Ind. Heye Found., v. in.) Klaatsch, Hermann 1908 The skull of the Australian aboriginal. Rep. Path. Lab. Lunacy Dept. Sydney, v. I, pt. 3, pp. 43-167. Martin, Rudolf 1928 Lehrbuch der Anthropologic 2d. ed. Jena. Oetteking, Bruno 1920 Morphological and metrical variation in skulls from San Miguel Island, California. I. — The sutura nasofrontalis. Indian Notes and Monogr., v. vn, no. 2, pp. 51-85. 1923 On the morphological significance of certain cranio-vertebral variations. Anat. Rec, v. xxv, pp. 339-353. 1924 Declination of the pars basilaris in normal and artifically deformed skulls. Indian Notes and Monogr., Misc. no. 27. Sarasin, Fritz 1916-22 Anthropologie der Neu-Caledonier und Loyalty-Insulaner. C. Anthropologie. Berlin. 7 q £~ Q \ n 1 f u J C3 1 / University of Connecticut Libraries