Downloaded from http://trngl.lyellcollection.org/ at University of California-San Diego on January 15, 2016 YOUNG AND ARMSTRONG ROBROYSTON FOSSILS, 267 XXIV.—The FOSSILS of the CARBONIFEROUS STRATA of the WEST OF SCOTLAND. By JOHN YOUNG, Vice-President, and JAMES ARMSTRONG, formerly Honorary Secretary. (Read 13th March, 1873.) INTRODUCTION. IN the introductory remarks to our General Catalogue of the Carboniferous Fossils of the West of Scotland,* we pointed out the desirability of having lists prepared of the fossils found in each particular group of strata in the various localities where they occur, for the sake of comparison with similar lists from the same geological horizons at other places, stating that " it is only when stratigraphical lists of our fossils are prepared on some such exhaustive plan, that we will ever be able to arrive at anything like a correct notion of the alternate changes of condition under which the flora and fauna of the Carboniferous period existed, as indicated by its beds of terrestrial, fresh water, and marine strata." Our distinguished honorary member, Thomas Davidson, Esq., F.R.S., in a paper recently communicated to the Edinburgh Geological Society, f also urges upon its members the necessity of preparing local catalogues, such as those above indicated, and he points out the immense importance of Palaeontology to Geology, mentioning one or two instances out of numbers which he could adduce, to show where the correct determination of a few fossils has been the means of unravelling the age and position of strata, not only in Britain, but in distant regions of the globe. In making out these catalogues, therefore, we will endeavour, with the assistance of members of the Society, to give from time to time, in the Transactions, a record of the fossils found in the strata of a particular locality, so far as known, and we trust that when these are completed, they will help to show where a species is apparently confined to a particular stratum and locality, or is recurrent throughout a series of beds extending over wide tracts of the earth's surface. * Trans. Geol. Soc. of Glas., Vol. III., Supplement, 1871. t Trans. Edin. Geol. Soc, Vol. II., p. 184, 1873. 2 D Downloaded from http://trngl.lyellcollection.org/ at University of California-San Diego on January 15, 2016 268 TRANSACTIONS OP THE GEOL. SOC. OP GLASGOW. It is our intention to give figures and descriptions of several new species contained in our cabinets, as well as to figure some of the rarer forms, and those also of which imperfect representations are given in the works of other palaeontologists. No. I. ROBROYSTON. Robroyston, the district from which we give the first special catalogue, is historically known as the locality where Sir William Wallace was betrayed into the hands of the English, in August, 1305. It lies about three miles to the north-east of Glasgow, and near the summit of that undulating tract of country which separates the valley of the Clyde on the south from that of the Kelvin on the north. Robroyston may be reached from Glasgow, either by the Garngad and Provan Mill Road, or by train to Bishopbriggs, and thence eastward by the village of Auchenairn. The limestone beds formerly worked there are termed the "Robroyston Limestone Series," but are known by other local names in its various outcrops, both north and south of the Clyde. It is what is termed a "calm" limestone, being of fine, compact texture, and bluish-grey colour when newly broken, but changing into a yellowish-grey on exposure, from the presence of iron. In this district the limestone averages from five to six feet in thickness, and is parted into two beds by a thin layer of shale. It is not very rich in fossils, the organisms being chiefly confined to a few species of Brachiopods and Cephalopods, with an occasional Crinoid stem, etc. But the bed of shale lying immediately over the limestone has yielded a considerable number of species, as will be seen from the list. A few feet under the limestone there is found a bed of coal of varying quality and thickness. It gradually thins along its southern outcrop in this district to a foot or less, while to the north it thickens considerably, and is found in the Kirkintilloch and Campsie districts to be seven and five feet respectively. The limestone at Robroyston was formerly worked in open-cast quarries on the farms of Hillhead, Barmulloch, and at other places in the neighbourhood. From the old shale heaps at these deserted quarries, specimens of the fossils may still be collected, while, by washing and carefully examining the weathered shale, abundance of the smaller organisms may be obtained. Occasionally the limestone and shales are passed through in the pits put down to the Possil upper black-band ironstone worked Downloaded from http://trngl.lyellcollection.org/ at University of California-San Diego on January 15, 2016 YOUNG AND ARMSTRONG—ROBROYSTON FOSSILS. 269 in the neighbourhood, and at these places the fossils characteristic of the strata may be obtained when these pits are being sunk. The Robroyston limestone is overlapped to the eastward by a series of sandstones and shales, stated to be the representatives of the millstone grit, this limestone being made the line of division in the new map of the district prepared by the Geological Survey, between that group and the upper limestone series of this portion of the Lanarkshire coalfield. The equivalent of the Robroyston limestone has long been extensively worked in the neighbouring districts of Garnkirk, Chryston, Bedlay, and Moodiesburn, chiefly as a flux for iron-smelting. It has also been passed through in pits in the parishes of Campsie, Kirkintilloch, and Cumbernauld. On the eastern border of the Lanarkshire coalfield it is found at various places in the Carluke district, having been worked at Gare and Westerhouse in former years. From these places large and interesting collections of the fossils found in the shale have been made, which agree very closely in genera and species with those found at Robroyston. South of the Clyde it is worked in the district around Thornliebank, Pollokshaws, and Barrhead, in open-cast quarries. Its equivalent is also found at Iimekilnburn, south-west of Hamilton, as well as in other districts in and around the borders of our Western coalfield, where, perhaps, it has not yet been so correctly identified, owing to local changes in the composition of the strata, and slight variations in the group of fossils. As formerly stated, the fossils are chiefly contained in the overlying shale, which is of a light grey colour at its junction with the limestone, but gradually changes as it passes upwards into a dark grey shale, in which they are much less abundant. The great majority of the larger species exist in a broken, fragmentary, or crushed condition, as is commonly the case in the soft limestone shales of most localities; still, perfect examples of many of them have been obtained, while all have the original shell-structure very well preserved. None of the comparatively few species found in the limestone are known to be different from those in the shale. It will, how­ ever, be seen from the list, that the number of species inhabiting this part of the old Carboniferous sea-bottom had very much increased in both genera and species by the time when the over­ lying shale was deposited. From the greater absence of Corals and Polyzoa in the Robroyston limestone and shales, than in Downloaded from http://trngl.lyellcollection.org/ at University of California-San Diego on January 15, 2016 270 TRANSACTIONS OP THE GEOL. SOC. OF GLASGOW. many of the other Scottish limestone strata, it would seem that the beds were laid down in water of very moderate depth, and that the conditions were not so favourable for the growth and development of these classes as in the formation of some of our other limestones. The structure and composition of the limestone also show that it could not be a very deep-sea deposit, a considerable per centage of clay having been mixed with the lime during deposition, while the comparatively few fossils met with in the stone clearly proves that the stratum was not built up by the growth and decay of organisms, like some of our richly- fossiliferous limestones, it being, like many of our other " calm" or "cement" limestones, formed to a large extent from the chemical precipitation of lime in the sea water—these, likewise, containing very few fossils. The underlying coal-bed indicates that land conditions must have prevailed to a large extent over the Lanarkshire coalfield, prior to the deposition of the limestone; and the intermediate strata, from its fossils, seem to point to fresh or brackish water conditions having obtained during the interval when the coal-bed was being gradually depressed, and the period when the intervening strata were finally covered by the sea. The following sections of a pit sunk to the coal under the Robroyston limestone at Balquarhage, near Campsie, will show the relation of the various strata more clearly than any now to be obtained at Robroyston old quarries. Feet. Inches. Surface soil and boulder clay, 7 0 Dark grey shale, with a few marine shells, 42 0 Light grey shale, with numerous shells, Trilobites, Crinoidea, etc., 3 0 Light grey shale, passing gradually into limestone, with fewer fossils, 1 0 Calm limestone in two beds, parted by layer of grey shale; fossils rather rare, 8 0 Grey calcareous shale, passing upwards into limestone, with very few fossils, 1 0 Bituminous shale, with a few obscure plant remains, ..