^^^^EM0IR8 OF THE GEOLOGICAL SUKVEY, y^t.0 SCOTLAl^D^, THE MESOZOIC ROCKS OF APPLECROSS, RAASAY, AND .NORTH-EAST SKYE, BY (t. W. LEE, D.Kc, • WITH CONTRUiUTION^l AND A\ ArPENlUX IJV S. 8. BUCKMAN, F.G.S. rtJBLISHIiD BY OEDBK OF THE LORDS COMMISSIONERS OF HIS MAJFSTy'k TIIEASUIIY, edinburgh : pkinted under the authority ov ills majesty's stationp:ky office By MORRISON & GIBB, LIMITED, Tanweu.. And to be purchased from E. STANFORD, 12, 13 iiml 14 Lokg Acre, Lonpon ; W & A. K. JOHNSTON, LIMITED, 2 St. Andrew Square, EtiiNDURfiji • HODGES, FIGGIS & CO., LIMITED, 104 Grafton Street, Dublin. From any Agent fprtlie sale of Ordnance Survey Ma^is ; ■ Or through any Bookseller, or from tlie Director General, Ordnance Survey Office.. Southaniiiton. 1920. Price Six Shillings Net. \\ \\ s (0 1 1 / s / / '^/ \ \\\ \ I '^ '«^. \ ■w \ ' I o CO / i^ ^ t 1 3n / •■' \v.. _ ._ W s \\ a ' *— — ""v. near the workings — i.e. at the southern end of the field — is in the form of silicate. At the north-eastern edge of the outcrop, that is N.E. of Dun Caan, the seam is seen to thin out to an unworkable thickness. Likewise ia Skye the seam is much poorer and considerably thinner. Samples collected at these two extreme localities from what is un- Baasay Ironstone, 87 doubtedly the same continuous seam, show a most radical difference : both in Skye and in N.B. Raasay the ooliths are almost entirely of carbonate, and the green silicate is practically absent. (PI. VII., Fig. 2). The carbonate is predominantly siderite ; calcite also occurs sparsely here and there, generally as an external cortex round the siderite. Owing to the difficulty of distinguishing between siderite and calcite in thin sections without the aid of chemical tests the proportion of calcite was erroneously exaggerated in the writers description of the plate accompanying Mr. Thorneycroft's paper {op. cit.). The ooliths are of two kinds : some are plain spherical or ovoid grains without concentric arrangement, while others have the typical zonal arrangement. Those of the first kind have a granular structure, and sometimes contains small dark black specks which suggest mag- netite, but otherwise look fresh and undecomposed. The concen- trically built ooliths consist of more or less transparent siderite or of siderite alternating with a brownish semi-opaque substance, in which faint remnants of the green chamosite can occasionally be detected. The ooliths — which in the case of the green silicate rock are easily extracted, thus permitting a separate analysis — are firmly embedded in the matrix, and it would be a difficult matter to analyse them as thoroughly as was done with the sample discussed in the preceding pages. Still, the main fact is established that while in the workable field much of the ore is in the form of the silicate chamosite, the seam passes laterally into a carbonate deposit, with traces of pre- existing silicate. How the alteration was brought about is not explained, though it seems clear that we are dealing here with a process different from that usually observed, in which a carbonate is the first stage in the evolu- tion of the ore. As regards its date, the only inference that can at present be drawn rests on the fact that the shaly strata which overlie the seam are lithologically uniform whether the ore is chamosite or carbonate. It can then be surmised that the change took place before the deposition of these shaly beds. The process would not necessarily imply a short period of time, because, as Mr. Buckman found from the fauna, there is a great stratigraphical break between the top of the ironstone and the shales that immediately succeed. In other words, the change may have taken place between the middle of the Whitbian and the end of the Yeovilian, which represent the extent of the strati- graphical gap. From what precedes it will have been seen that definite conclusions regarding the genesis of the ore are not yet established on all points, but it is hoped that more may come to light as the workings extend further into the field, thus affording means of following possible varia- tions in the constitution of the seam. Should, for instance, the galleries reach a point where the green ore were to be seen passing into car- bonate, special investigation at the junction of the two might yield much of the evidence which is so far lacking for a proper understanding of the problem. Specimens from the working face, obtained by Dr. J. S. Flett in June 1917, representing the average type of the ore as then extracted, still belong to the green oolitic ore. The only difference from the ore at the outcrop is that the proportion of echinodermic calcite appears higher, the calcite being in large, glossy fragments. 3& Upper Lias. The Iron-Ore Field. — The extent of the Upper Lias as known to Woodward is represented on the Geological Map on the scale of 1-inch to the mile, published by the Geological Survey in 1896. The detailed investigations undertaken by Mr. W. Thorneycrof t, with the assistance of Mr. C. B. Wedd, have necessitated certain modifications in the mapping of the outcrop, and these are shown in the new edition of the map. An account of the results of their investigations was placed before the Geological Society of Edinburgh by Mr. Thorneycroft,* together with useful information on the Upper Lias of the Hebrides generally. Several bores and trial excavations were put down by Mr. Thorney- croft and also by Messrs. Baird along the southern edge of the field, the configuration of which is therefore now accurately known. These bores and excavations have shown that the seam is of workable thick- ness along the southern edge of the main field, that is from Churchton Bay towards the path to Dun Caan above Hallaig. It is also pre- sumably of workable thickness in the faulted outlier of Beinn na' Leac, but this area has not yet been investigated, with the exception of one excavation made at Rudha na' Leac. Exposures and trenches dug east and north-east of Dim Caan show that the seam thins out and disappears northwards along the east coast. Actual exposures do not occur in the two miles of cliff south of Screapadal, but from the complete absence of loose blocks of ironstone it may be safely inferred that the seam is absent, as noted further south. To sum up, we know that at, and near, the southern edge of the main Upper Lias area the ironstone is workable, while it is too thin or absent along its eastern margin. The central portions of the area have not been tested by borings : consequently we are in entire ignorance of the extent and value of the concealed field lying north of the southern margin. The proving of the north-western portion of the area would necessitate bores of considerable depth. Assuming the thicknesses measured on the east cliffs to hold good, the Upper Lias would lie some 670 feet below the surface at Storav's Grave (the small patch coloured as Upper Lias near Storav's Grave on the first edition of the map belongs to the base of the Great Estuarine Series). The structure of the proved portion of the field permits at present, and for a considerable time to come, of a relatively simple mode of ex- ploitation. Starting from a low level, galleries are driven up the dip, which thus creates a natural outflow fpr the water without pumping. Likewise the ore is carried direct from the working faces to the pier down the incUne. Carriage is effected by a Ught tramway, the motive power being transmitted to the hutches by an endless cable. North-East Skye. The fullest visible development of the Upper Lias in N.B. Skye is towards the base of the cliffs and slopes between the entrance of Portree Bay and the islet of Holm. The soft shaly materials of the Upper Lias, occurring at the base of great superincumbent masses of rock, are mostly talus covered, and there are no clear natural sections. * " Note on the Upper Lias of the Western Islands in reference to the Iron Ore Deposit therein." By Wallace Thorneycroft. Trans. Edin. Oeol. Soc, vol. x., Part ii., p. 196, 1914. North-East Skye. 39 Here and there a bare patch occurs, and a general estimate of the thickness can be made by calculating the distance from the top of the Scalpa Sandstone to the base of the Inferior Oolite. Most of the evidence used here is based on the information from boring operations supplied by Messrs. Baird & Co., and from excavations made by Mr. D. Tait in the course of his collecting work for the Survey. The thickness varies considerably : in a bore put down near the mouth of the river Bearreraig there are 78 feet of strata between the top of the ironstone and the top of the Scalpa Sandstone. As measured by Mr. Tait along a trench he made three-quarters of a mile south of Holm the corresponding thickness is 48 feet, and it does not appear to be less than that anywhere north of Portree Bay. This does not include any portion of the top of the Scalpa Sandstone which might conceiv- ably prove to be of Upper Lias date as is the case in Raasay. This great thickness, compared with the development in Raasay, is a striking feature, when one considers the short distance between the two areas and the fact that the same zones are involved : hence Mr. Buckman proposed the name " Portree Shales " for these Upper Lias shales.* The strata consist of dark micaceous shale, generally soft and friable, with occasional harder bands and limestone nodules. The basal portion of the shale is so covered by debris or inaccessible that the details of its fauna could not be ascertained, although its litho- logical characters are known from the boring records of Messrs. Baird & Co. The lowest point from which detailed search was made is 14 feet above the top of the Scalpa Sandstone. At this level, three- quarters of a mile south of Holm, Mr. Tait made the interesting dis- covery of a thin band of jet in close proximity to which ammonites were found : Harpoceras afi. exaratum (^. and B.) and ? Elegantuliceras elegantulum (Y. and B.) which indicate the Exaratum Zone. The well-known Jet Eock horizon of Yorkshire is in the Exaratum Zone, and the similarity of conditions in widely separated areas like York- shire and N.E. Skye is truly remarkable. In the unexplored portion below the Jet band there is ample room for deposits of the Tenuicostatum Zone. The Exaratum fauna continues for some 2 feet above the jet ; apart from the ammonites just mentioned the only other fossil found is a lamellibranch resembling Astarte suhtrigona Goldfuss. The rest of the series, about 30 feet thick at the point specially searched, belongs to the Falciferum Zone. Here, the fauna of the Falciferum Zone consists for some 10 feet of ammonites mainly : Dactylioceras cf. anguinwm (Rein.), B. cf. crassiusculum (Simp.), D. cf. holandrei (d'Orb.) and Harpoceras aff. mulgravium (Y. and B.). A line of lime- stone-nodules which follows has yielded D. cf. gracile (Simp.), Z). cf. holandrei, Coeloceras ci.foveatum (Simp.), Harpoceras of the mulgravium- and falciferum-tYpe, and Harpoceratoides ; two gasteropods were also obtained : Natica adducta (Phill.) and a depressed form of Pleuroto- maria with the shape of P. actinomphala (Desk). In the shale in which the nodules are embedded Phylloceras and D. gracile ? were also found, accompanied by Astarte, Lucina and Inoceramus. Nodules 3 feet higher up are rich in Dactylioceras, especially D. cf. vermis (Simp.). Rusty, decalcified nodules occurring at two intervals a few feet higher up, are characterised by the same species. D, cf , holandrei * See Appendix, 40 Upper Lias. recurs in abundance higher up, accompanied by ? Pseudolioceras and cf . Harpoceras. D. cf . athleticum was found 2 feet above this. No records are at hand regarding the fauna — if any — of the shale between the last-mentioned point and the representative of the Raasay Ironstone, which at the locality under consideration occurs 8 feet above. Here it is 2 feet thick ; in the boring put down by Messrs. Baird near the mouth of the Bearreraig river its thickness was found to be 5 feet 9 inches. It is a greenish ferruginous oolitic limestone or low grade ironstone, different in composition from the green stone of Raasay. The iron in the Raasay workings occurs in the form of a silicate, while here it is as carbonate — at least as regards its main mode of occurrence, viz., ooliths. In a sample analysed by Messrs. Baird the average iron-percentage was 11 '96 per cent., which is obviously too low for economic purposes. It is not so richly fossili- ferous as the ironstone in Raasay ; the only fossils observed are belemnites belonging to Dactyloteuthis digitalis (PhiE.). Several examples are obviously worn and rounded, pointing to a remanie condition which would support Mr. Buckman's suggestion that the Raasay ironstone is a remanie deposit. Above the ironstone the shale becomes harder and less argillaceous, and its fauna is that of the Aalenian stage, showing that, as in Raasay, there is a considerable gap cutting out the Yeovilian and part of the Whitbian. Upper Lias strata occur at several places along the coast south of Portree Bay. They were noted and described long ago by Bryce (pp. cit., p. 322). They appear everywhere much thinner than in the district near Holm, but there can be no doubt that here all the sections are incomplete. The soft Upper Lias shales have been practically " squeezed " between the massive Scalpa Sandstone and the heavy superincumbent masses of Inferior Oolite which have slipped along low hade planes or lines of dislocation which are so common in Ben Tianavaig. What there is of the Upper Lias is very fossili- ferous : small Dactylioceras and large Harpoceras are abundant. Lenticular masses of limestone, sometimes pyritous, occur here and there. H. B. Woodward noted the presence of " annulate ammonites " in the top layers of the Scalpa Sandstone, which would mean that the Upper Lias fauna begins to appear in that sandstone as it does in Raasay. No representative of the Raasay Ironstone was observed. Comparisons with other Scottish Districts. — Owing to the importance of the Raasay Ironstone deposit it may not be out of place to give here a brief account of the Upper Lias in the other Jurassic areas of Scotland. Inquiries are sometimes made as to whether the ironstone is represented in these Upper Lias strata ; and it can be asserted that there is no ready supply of the ironstone outside Raasay. Mr. Thorneycroft has dealt with the subject in his paper already quoted, and his views are in harmony with those of the present writer. At Carsaig, in the south of the Island of Mull, there is a small tract of Upper Lias, with no indications of ironstone. Beyond quite thin ribs and nodules of clay ironstone there is likewise no deposit in the Upper Lias of the south-east part of Mull, namely, between Loch Buie and Loch Spelve, and in the Loch Don district. Skye and other Districts. 41 The Kilchoan district of Ardnamurchan was visited in the company of Messrs. Thorneycroft and Wedd, also without results. In Eigg the position of the Upper Lias must be at a considerable depth below sea-level. In the south-east of Skye the ironstone condition is represented by a ferruginous limestone seen in a section north of Dun Liath. The un- promising nature of the ironstone outcrop in north-east Skye has already been indicated, and there remains to consider the possibilities of the con- cealed portions of the field. There is no reason to suppose that the Upper Lias does not extend under the whole of the north of Skye, and ironstone formation, as in Raasay, may conceivably have recurred at various points within that vast tract. Unfortunately the depth to be expected is everywhere — except in the vicinity of the outcrops — so great that the proving of the field by boring operations would be an expensive matter, and the probability of the development of any ironstone found would be most unlikely under present economic conditions. Taking into consideration only those points where borings could be started in Jurassic rocks beneath the covering of basalt, the least unpromising would probably be the Ollach coast, as it is the nearest to the Raasay field, but in order to reach the Upper Lias the whole thickness of the Inferior Oolite would have to be passed through : a matter of perhaps one hundred fathoms. Going northwards beyond the Holm district — which has been tested — the depth of the Upper Lias would gradually increase from a few fathoms at Bearreraig to the full thickness of the Inferior Oolite at Inver Tote, beyond which, in the direction of Stafiin, an increasing thickness of Great Estuarine Series sediments would have to be added. The Upper Lias would thus be some 150 fathoms below sea-level at Stafiin. A similar estimate applies to the other exposed Jurassic tracts of North Skye, namely, Monkstadt, Uig and Loch Bay, which were examined by the writer and all found to be high up in the Estuarine Series. The Upper Lias is nowhere exposed in the Jurassic areas of the East of Scotland, and there is hardly any hope it might be reached by borings of moderate depth. At the most favourable points — namely, in the Brora district — the position is concealed through the action of faulting under the whole of the Inferior Oohte and part of the Great Oolite. It is true that we are in ignorance of the nature of the greater part of the sediments of the Inferior Oolite in the East of Scotland, little of which is exposed, but since in that region the Jurassic rocks as a whole evince distinct littoral and estuarine conditions of deposit of considerable thickness it seems unlikely that the Inferior Oolite could be less thick here than in Raasay and Skye. Thus depths of over a hundred fathoms would have to be expected in order to reach the position of the Upper Lias. [Addendum to p. 37 : — In " Die Versteinerungen der Eisenerzformation von Deutsch- Lothringen und Luxemburg," Abhcmdl. z. geol. Specicdkarte von Elsass-Lothringen, N.F., Heft vi, 1905, p. 20, E. W. Benecke considers that the Lorraine ore was originally deposited as a Leptochlorite (Thuringite, Chamosite, etc. ), as appears to be the case here.] CHAPTEE VI. INFERIOR OOLITE. AALENIAN TO VESULIAN. Raasay. The Raasay Ironstone of Upper Lias date is succeeded by some 70 feet of micaceous shale which former observers, namely, Prof. Judd and H. B. Woodward, had attributed to the Upper Lias. Recent survey work has shown to Mr. Buckman that there is a stratigraphical gap above the ironstone. This gap includes part of the Whitbian and the whole of the Yeovilian. Adopting the classification now in use in the strati- graphical scheme of the Jurassic Rocks of England, these micaceous shales of Raasay would belong to the base of the Inferior Oolite, that is, to the Aalenian stage. Woodward's " Basement Beds " come higher up in the sequence. Their allocation to a position corre- sponding to the " Midford Sands " was due to the faulty identification of some ammonites, since then identified anew as proper Inferior Oolite forms. The materials excavated when driving the gallery to the Main Mine have yielded good evidence, showing the relations between the Upper Lias and the Inferior Oolite. From shale on top of the ironstone, and under a sill which produced induration, Mr. Tait obtained the ammonites Pleydellia svbcompta (S. Buck.), WalJcericeras burtonense (S. Buck.) and Cotteswoldia cf. limatula S. Buck. These belong to Aalenian forms, and they show that the Aalensis Zone rests non-sequentiaUy on the ironstone, and that there is a big gap : all the Yeovilian and part of the Whitbian missing ; as mentioned elsewhere the same succession occurs in N.E. Skye. The Inferior Oolite of Raasay consists of two lithological divisions : a great mass of sandstone 600 feet thick, resting on a series of shale from 20 to 70 feet thick, which is the shale just referred to above. This shale of the Aalensis Zone offers few actual exposures, but it forms a well-defined sloping feature almost everywhere at the foot of the great sandstone. It attains its greatest thickness on the east side of the island, at the foot of Beinn na' Leac and at the foot of Dun Caan, while it is thinnest in the area near Inverarish. From the conspicuous feature it makes at the foot of Dun Caan, Mr. Buckman has proposed for it the designation " Dun Caan Shales," which may be usefully employed. Although natural exposures are few and disconnected, the Survey is in possession of very satisfactory evidence regarding the fauna of the shale, thanks to the excavation work undertaken by Mr. Tait at the foot of Dun Caan, where over 70 feet of shale were examined in detail. The fossils collected at this locality show that_49 feet of strata Inferior Oolite (Baasay). 43 belong to the Aalensis Zone proper, while in 16 feet of strata above Mr. Buckman recognises faunal changes which induce him to establish an " Upper Aalensis " or " Venustula " Zone. By far most of the fossils obtained from the Aalensis Zone are ammonites ; belemnites come next in order of abundance, while other groups are only represented by a few lamellibranchs. Of the ammonites, specimens of Cotteswoldia are the most abundantly represented ; they belong to C. costulata (Ziet.), C. attrita (S. Buck.), C particosta S. Buck, C. subcandida S. Buck, and C. superba S. Buck., with doubtful representatives of C. venustula S. Buck., near the top. The zone-fossil Pleydellia aalensis (Ziet.) was found, though sparingly, accompanied by P. leura (S. Buck.) and ? P. subcompta (Branco), and an example of the distinctive Pleurolytoceras leckenbyi (Lye.) was obtained from the top of the zone. Other ammonites are Canavarina digna S. Buck., G. sp., C. folleata S. Buck., Walkericeras delicatum S. Buck., and W. sp., prior to W. burtonense. Among the belemnites a form resembling Dactyloteuthis irregularis (PMIL), but much thinner, Megateuthis tripartitus 1 and M. cf . tripartitus incurvatus (Benecke) were found. Other groups of organisms are very scarcely represented : the only species observed are Inoceramus cf. cinctus Miinster, and an Astarte of excavata type, with few, strong ridges. The Upper- Aalensis Zone — which Mr. Buckman proposes to call the " Venustula " Zone — was examined both at the locality to which the foregoing remarks apply, and a few hundred yards further north, at Druim an' Aonaich. The stratal lithology difiers only in the frequent presence of limestone-nodules, and the faunal facies is similar, except that most of the species are different. As lower down, ammonites predominate : Canavarina digna S. Buck., C. venustula S. Buck., an ammonite resembling Cotteswoldia misera S. Buck., and another like a form described on Plate XXXI., Pig. 7, of Mr. Buckman's Mono- graph on the Inferior Oolite Ammonites, Pleurolytoceras leckenbyi (Lycett) P hircinum (Quenst.), Walkericeras subglabrum S. Buck., and doubtful examples of ? Cypholioceras cf. opaliniforme S. Buck., of Pseudolioceras cf. beyrichi (Schloenb.), and of Pleydellia. The lamellibranch Posidonomya bronni Voltz, was observed in different layers here as well as in the core of a bore midway between Dun Caan and Inverarish. Inoceramus and I/ucina cf. crassa J. de C. Sow., occur sparingly, and also the belemnite Pseudobelus subclavatus (Voltz). About five feet of shale with calcareous nodules and hard bands separate by gradual transition the shale of the Aalensis and Venustula Zones from the overlying great sandstone mass The fossils obtained from this horizon at Druim an' Aonaich were allocated by Mr. Buck- man to the Opaliniformis Zone. The fossils obtained are : ? Lucina crassa /. de C. Sow. Cypholioceras opaliniforme S. Buck. CanavareUa ? (or a new form ?) Pleydellia cf. subcompta {Branco) Pleydellia sp. Pleurolytoceras hircinum (Quenst.) Pseudolioceras beyrichi {ScMoenb.) Walkericeras subglabrum {8. Buck.) Megateuthis tripartitus brevis (Quenst.) „ „ oxyconus (Quenst.) 1 1 2 10 8 3 44 Inferior Oolite. A large specimen of Nautilus jurensis ? Quenst., found loo?e, belongs probably to this horizon. The above remarks exhaust the information collected from the Inferior Oolite shales, and the great sandstone will be considered next. The lower portion of the sandstone is more or less calcareous for some 50 feet, and the actual base is often marked by a thin lime- stone a few feet thick, sometimes ferruginous and rusty - looking. This basal limestone-horizon has been examined at several localities, of which the most fossiliferous is on the path one mile south of Dun Caan, where the following section is to be seen : — rt. In. Calcareous sandstone Thin bedded limestone passing up into the above Limestone with fossiliferous lentioles full of ammonites Shaly Umestone ....... Limestone with belemnites ..... Thin bedded shaly Hmestone ..... Shaly limestone with belemnites and lamelli- branohs . . . . .10 Talus, grassed over (Venustula Zone) These different beds are not clearly separated from each other, and the zones comprised within therti are evidently very close together and not marked by lithological differences. The bulk of these beds, up to the limestone with lenticles, belong to the Scissum Zone. The limestone with belemnites, 8 inches thick, has yielded : Pecten demissus Phill. „ (Amussium) paradoxus Ooldf. Megateuthis conoideus {Opp.) „ ventralis ? (Phill.) voltzi ? {Phill.) Pachyteuthis breviformis {Phill.) The limestone with fossiliferous lenticles is very rich in small ammonites of the Scissum Zone, besides a few lamellibranchs. The following fossils were obtained : — Khynohon elloidea cf. krammi {Ben.) Gresslya abduota {Phill.) Pecten (Amussium) paradox s Ooldfiiss Pteria sp. Cf. Ancolioceras substriatum S. Buck. Of. CanavareUa. Lioceras oostosum {Quenst.) „ gracile S. Buck. ,, partitum 8. Buck. ,. subcostosum 8. Buck. „ uncinatum 8. Buck. „ lineatum ? 8. Buck. „ cf. bifidatum 8. Buck. „ cf. comptum {Rein.). „ cf. opalinum {Rein.). „ cf. partitum 8. Buck. ,, cf. pUcatellum iS. Buck. „ cf. undulatum 8. Buck. „ sp., between unoum and gracile S. Buck. Rhaeboceras cf. tortum 8. Buck. This ammonite-fauna shows many points of resemblance to that from the Ardnadrochet Glen, Isle of Mull, which was examined for Baasai/. 45 the Geological Survey by Mr. Buckman. The small Pecten paradoxus occurs here in nests, as is the case in Mull, and many of the ammonite- species are identical. Owing, perhaps, to the lenticular nature of its fossUiferous portions the zone often escapes detection in Raasay. For instance, east of Dun Caan its position is clearly seen, but the rock is less calcareous and fossils scarce. In his " Notes on the Upper Lias of the Western Islands," * Mr. W. Thorneycroft mentions the presence of a bed of ferruginous limestone at the top of the Upper Lias. What was known as " Upper Lias " at the time he made his observation is the shale just described as belonging to the Aalensis and Venustula Zones, and the ferruginous Umestone found by him probably belongs to the Scissum or to the Murfhisonse Zone, more likely the latter than the former. This ferruginous facies f was noted at the foot of Dun Caan and in the bed of the Inverarish Burn near the ordnance datum point 533 on the 1-inch Map, where it contains many belemnites. There are only faint suggestions of the Ancolioceras Zone. The presence of the Murchisonae Zone was recorded at several localities in Raasay, the best from the point of view of collecting being the section along Dun Caan path just described. Here fossils of the Murchisonae Zone were found 3 feet above the Scissum Zone. The relations of the Murchisonae to the Scissum Zone are clear, but great difficulty was met in separating the Murchisonm bed from those of the Bradfordensis, Concava and Discites Zones, which are very close to it and difficult to distinguish by field features. Small local dislocations, not easily detected, would increase the difficulty. That these zones are represented by very little sediment is shown by the fact that fossils representative of them were found in the same block. The fauna of the Murchisonae Zone consists mainly of small ammonites. Gresslya abducta (PJiill.) Of. Isooardia cordata J. Buck. Pecten sp. Apedogyria suboornuta 8. Buck. „ sp. nov. „ ? patellaria S. Buck. Criokia reflua 8. Buck. Hyattia wilsoni S. Buck. Hyattina brasili 8. Buck. Ludwigia murchisonse (/. de C. Sow.) „ IsBvigata ? 8. Buck. '• Cf. Ludwigina patula 8. Buck. „ umbilicata 8. Back. Manselia subfaloata 8. Buck. New, cf. Paquieria. ? Pseudographoceras literatnm 8. Buck. ? Strophogyria pinax 8. Buck. Welschia extrala3vis (Quenst.) ,, obtusiformis