258 Rev. P. B. Brodie on the Geology of the 



of Gloucestershire*) conceive it to be not sufficiently distinguish- 

 able from it to entitle it to rank as an independent formation. 

 But from the facts and sections given in Mr. Morris's paper, 

 they seem to be as closely intermingled; indeed he distinctly 

 states that the slate is not independejit of the Great Oolite, and 

 thus confirms our views respecting its characters in Gloucester- 

 shire. The bed of clay, which we suppose to be the representative 

 of the ' Bradford clay,' does not occur at Colly wcston overlying 

 the slate, though it may have been pre\iously denuded. 



Fossils generally are not very abundant in the Collyweston 

 slate, and these consist almost entirely of marine shells, among 

 which Trigonia im.p7'essa (a highly characteristic shell), Gervillia 

 acuta (a gregarious species, lying grouped together on the slabs, 

 but not commoQ in the Cotswolds), Cardium, Pinna, Pecten, and 

 a small Natica, are the most frequent, though a few others are 

 mentioned by Mr. Mo)'ris. He also notices numerous frag- 

 ments of Pecopteris poli/podioides, a species of fern abundant in 

 the oolitic shales of Yorkshire, which seems to identify the slate 

 with them. Plants however, as far as my observation went, are 

 comparatively rare at Collyweston, and very imperfect. I walked 

 over tons of slate laid out for weathering, as in Gloucestershire, 

 and I could not observe even a trace of vegetable matter, the 

 slate being in most cases particularly unfossiliferous, and on this 

 account much better adapted for (Economical purposes. Two 

 genera of plants only are mentioned by Mr. Morris, Pecopteris 

 and Zamites, and these in patches and fragmentary, scattered 

 through certain portions of the beds overlying the slate. But 

 these must be limited to particular spots, for in the four quarries 

 I visited on Collyweston Hill I saw scarcely a trace of any, and 

 I was struck by their apparent rarity in that district, compared 

 with their abundance in certain divisions of the slate at Seven- 

 hampton and other localities near Cheltenham. The absence of 

 the varied flora so characteristic of the slate near Cheltenham 

 and Oxford, is not more remarkable than is that of the other in- 

 teresting terrestrial and marine remains which it there contains. 

 I saw no teeth or bones of reptiles and fish, nor elytra of beetles, 

 nor could I learn that the workmen had ever observed any ; and 

 hence zoologicalhj the Collyweston slate drifers more from its 

 south-western equivalents than it does in its internal mineralo- 

 gical structure. These facts lead to the inference that it was 

 deposited beneath a deeper sea, and at a greater distance from 

 land, whence we should expect to find few evidences of neigh- 

 bouring coasts, and a larger assemblage of marine exuviae, the 

 denizens of deeper water, though the genera would not be very 

 numerous. 



* See Quarterly Journal of the Geological Society, No. II. p. 220. 



