Fig. 3. Pecten Suttonensis, Tawn. Sutton and Southerndown series. 4. Etheridgii, Tawn. 7. 8. 9. Sutton and Southerndown series. - planicostata, Tawn. Sutton series. Sutton and Southerndown series. 10. Anomia socialis, Tawn. Sutton series. PLATE IV. Fig. 1. Ammonites Dunravenensis, Tawn. Sutton series. 2. Cardinia ingens, Tawn. 3. Suttonensis, Tawn. 4. Astarte Duncani, Tawn. Sutton series. 5. Anatina precursor, Quenst. Sutton series. Sutton series. 6. Cardita rhomboidalis, Tawn. Avicula-contorta sandstones. 9a, 9b. Patella Suttonensis, Tawn. Sutton series. 10. Natica Pylensis, Tawn. Avicula-contorta sandstones. 2. Notes on a SECTION of LOWER LIAS and RHETIC BEDS, near WELLS, SOMERSET. By the Rev. P. B. BRODIE, M.A., F.G.S. THE accidental lowering of a road at Milton Lane, one mile and a half north of Wells, exposed a very interesting section of Lias and Rhætic beds, which has not been referred to by Mr. Dawkins in his paper "On the Relations of the Liassic and Rhætic Series in Somersetshire." This section is the more deserving of notice because, as a general rule, the sections in the immediate neighbourhood only exhibit the White Lias and Rhætic beds, and these have not hitherto been recorded so near the city in a northerly direction, nor so close to the Mendips; and in this case we have the "Lima-beds" the highest scen, passing into and overlying the White Lias and the Avicula-contorta zone. The nearest section to Wells described by Mr. Dawkins, showing the White Lias and Rhætic series, though very obscure, is at Pen Knowle, about five miles west of the town. The Milton-Lane section gives a clearer view of the succession of the "Lima-beds" downwards, and I can confirm Mr. Dawkins's* statement that the "White Lias" rests immediately upon the Rhætic beds+; for whether the strata below No. 4 in the annexed section, down to the "White Lias," belong to the "Lima series," which is most probable, and to which I have referred them, or form a reduced equivalent of the "Insect and Saurian beds," it is evident that the latter do not here or elsewhere underlie the "White Lias." The following is the section‡ at Milton Lane, in descending order:― *This was also pointed out by Mr. Bristow in his paper communicated to the Bath Meeting of the British Association. At Harbury, in Warwickshire, the Lima-beds rest immediately on the White Lias. This section was taken conjointly with my friend Mr. James Parker. White Lias. Lima-beds. Section at Milton Lane. 1. Thick blue limestones, compact, containing Lima gigantea, feet. inches. 5 0 0 4 0 2. Clay and bands of indurated rubbly limestone, often no- 4. Sandy limestones and intercalated shale, numerous fos- 6. White Lias limestone, hard, close-grained, containing the 7. Soft marly shale (base of White Lias), with Modiola mi- 8. A peculiar bed, with much quartz, broken and rubbly 10. Grey marl; with the exception of traces of small plants, 7 0 5 0 7 4 3 96 1 6 8 0 Rhætic Series. 2 6 11. Alternations of clay and marl, rather variable, about 3 or 12. Hard grey marl, similar to No. 15, becoming harder as it 2 13. Soft green marl and shale. 1 64 23 14. Series of grey and yellow marls, with layers of marl near The Lima-series here amounts to 27 feet, the White Lias to 10 feet 4 inches. The Rhætic (including the grey marls) to 18 feet 6 inches. I could see no trace of Ammonites planorbis, nor any of the peculiar limestones indicating the " Insect and Saurian" zones, which seem to be entirely wanting, the Lima-beds resting immediately upon the "White Lias." There is certainly a greater thickness of Lias at this spot than might have been at first sight expected, considering that, as a whole, it thins out towards the Mendips, with which it here comes into almost immediate contact. The direction of the lane is nearly at right angles to the strike of the beds, which dip about ten degrees, but somewhat irregularly, being much disturbed to the north-east. I found one piece of bone-bed lying loose at the lower end of the lane, near the bed No. 14, full of bones, teeth, * Most of the shells in nos. 1 & 4 were too imperfect for determination of the species, and scales of fish (Hybodus), &c. ; but after a careful search on several occasions, neither Mr. Parker, myself, nor the workmen could find any more, or discover its exact position in situ. The lithological character of this "bone-bed" was rather different from that which it usually presents, the bones and teeth being imbedded in a hard mass of limestone-conglomerate, made up of lighter-coloured angular fragments of limestone forming a kind of coarse breccia. On another visit to Milton Lane, after I had left Wells, Mr. Parker informed me that a further excavation nearer to the Mendips exhibited a slight difference in the stratum No. 8, which was much faulted and broken up, one side being let down, with an intervening band of dark shale belonging, I suppose, to the "Avicula-contorta zone." DECEMBER 20, 1865. Hugh Leonard, Esq., C.E., Calcutta ; William Lyon, Esq., J.P., Wellington, New Zealand; Moses Pullen, Esq., Painswick, Gloucestershire; and Charles Stavely Rooke, M.I.C.E., 12 Blenham Terrace, Leeds, were elected fellows. The following communication was read:— On the CONDITIONS of the DEPOSITION of COAL, more especially as illustrated by the COAL-FORMATION of NOVA SCOTIA and NEW BRUNSWICK. By J. W. DAWSON, LL.D., F.R.S., F.G.S., Principal of McGill College, Montreal. I. Introduction. [PLATES V-XII.] II. General Considerations relating to Physical Conditions. 1. Physical Characters of the several a. The Upper Coal-formation. d. The Lower Carboniferous e. The Lower Coal-measures. 3. Geological Cycles. 4. Summary of facts relating to the III. Details of the Character and Fossil e. Division 5. 1. Introduction. 2. Logan's Section. a. Division 1. b. Division 2. f. Division 6. c. Division 3. g. Division 7. d. Division 4. h. Division 8. IV. Remarks on the Animals and Plants whose remains occur in the Coal. 1. Introduction. 2. Coniferous Trecs. 3. Sigillariæ. 4. Calamodendron. 5. Calamites. 6. Asterophyllites, &c. 8. Megaphyton. 9. Lepidodendron. 10. Lepidophloios. 11. Cordaites, or Pychnophyllum. 12. Sporangites. 13. Tissues in the Mineral Charcoal. a. Bast tissue. b. Vascular bundles of Ferns. c. Scalariform vessels. d. Discigerous wood-cells. e. Epidermal tissue. 14. Rate of growth of Carboniferous Plants. 15. Bivalve Shells. 16. Spirorbis carbonarius. 17. Crustacea. 18. Fishes. 19. Land-animals. V. Appendix: Descriptive List of § I. INTRODUCTION. In several former papers presented to this Society, I have endeavoured to illustrate the arrangement of the Carboniferous rocks of Nova Scotia, and to direct attention to their organic remains, the structures found in their coals, and the evidence which they afford as to the mode of accumulation of that mineral. The present paper is intended as the summing up and completion of these researches, with the addition of the new facts resulting from a careful study of the microscopic structure of more than seventy beds of coal occurring in the South-Joggins section, and of the fossil plants associated with them. These results will, I hope, throw much additional light on some of the more difficult problems connected with the theory of the accumulation of vegetable matter in the Carboniferous period, and its conversion into coal. The subjects to which I propose to direct attention may be conveniently arranged under the following heads : (1) General considerations relating to the physical conditions of the Carboniferous period in Nova Scotia. (2) Details of the character and contents of the several beds of coal in the Joggins section, arranged in the order of Logan's Sectional List. (3) Remarks on the genera of animals and plants whose remains occur in the coal, and on their connexion with its accumulation. § II. GENERAL CONSIDERATIONS RELATING TO PHYSICAL CONDITIONS. 1. Physical Characters of the several Coal-formations.-The total vertical thickness of the immense mass of sediment constituting the Carboniferous system in Nova Scotia may be estimated from the fact that Sir W. E. Logan has ascertained by actual measurement at the Joggins a thickness of 14,570 feet; and this does not include the lowest member of the series, which, if developed and exposed in that locality, would raise the aggregate to at least 16,000 feet. It is certain, however, that the thickness is very variable, and that in some districts particular members of the series are wanting, or are only slenderly developed. Still the section at the Joggins is by no means an exceptional one, since I have been obliged to assign to the Carboniferous deposits of Pictou, on the evidence of the sections exposed in that district, a thickness of about 16,000* feet; and Mr. Brown has estimated the Coal-formation of Cape Breton, exclusive of the Lower Carboniferous, at 10,000 feet in thickness. When fully developed, the whole Carboniferous series may be arranged in the following subordinate groups or formations, the limits of which are, however, in most cases not clearly defined a. The Upper Coal-formation.-It consists of sandstones, shales, and conglomerates, with a few thin beds of limestone and coal. Calamites Suckovi, Annularia galioides, Cordaites simplex, Alethopteris nervosa, Pecopteris arborescens, Dadoxylon materiarium, Lepidophloics parvus, and Sigillaria scutellata, are among its characteristic vegctable fossils. * Quart. Journ. Geol. Soc. vol. i. p. 329. Ibid. vol. vi. p. 116. |