266 John Aitken. — Grit-rocks of North Wales. 



exposed for some time to the weather, without being struck with 

 the thought that it must, at a former period of the world's history, 

 have formed a portion of a great palseozoic coral reef, thus furnish- 

 ing conclusive evidence of a shallow sea and a change of conditions, 

 and which probably represents the first step towards that complete 

 change which resulted in the deposition of the arenaceous strata 

 which now rest upon this ancient sea-beach. 



Then, again, if we glance at the fossils discovered in the Oswestry 

 sandstones, a list of which, containing sixteen species, was given by 

 Mr. W. Prosser, F.G.S., in the year 1865 (page 110, Vol. II. of the 

 Geol. Mag.), to which Mr. D. C. Davies has subsequently furnished 

 six additional species, we shall find (with the exception of the 

 doubtful shell named Schizodus) that they are all forms found in, 

 and characteristic of, the Carboniferous Limestone. 



The fossils contained in the list furnished by Professor Phillips, 

 in his Geology of Yorkshire, and from the Millstone-grits of that 

 county, were principally derived from strata, which have, since he 

 wrote, been eliminated from that formation by a more recent classifi- 

 cation, and included in the Yoredale series ; consequently it has no 

 longer any value as determining the fauna pertaining to the Mill- 

 stone-grit group. 



In order to afford an opportunity of comparing the fauna found in 

 the shales interstratified with the Millstone-grits of the Northern 

 counties, with that from the grits on the Welsh border, before re- 

 ferred to, I may be allowed to quote the following passage, taken 

 from the inaugural address I delivered to the Manchester Geological 

 Society in November last.^ " The series of grits and shales of the 

 northern counties, has generally been considered as destitute of all 

 animal life ; more recent discoveries have, however, revealed to us 

 the fact, that, during the period of their deposition, the co-existing 

 fauna was by no means limited either in specific forms or individual 

 numbers ; true it is that the coarse sandstones of this series have 

 not as yet yielded auy undoubted examples of the animal life of the 

 period. On the other hand, the interbedded black carbonaceous 

 shales are gradually becoming known to geologists as the receptacles 

 of a varied fauna. From a layer of calcareous nodules enclosed in 

 a fossiliferous bed of higher Millstone-grit shales, at Eough Lee in 

 Pendle, I have succeeded in collecting five or six species of Gonia- 

 tites, two or three of OrtJioceratites, two of Posidonomya, two of 

 Avicidopecten, together with other forms ; in addition to which, the 

 late Mr. Joseph Whitaker of Burnley obtained two small Gastero- 

 pods and a fish tooth of the genus Cladodus. More recently, Mr. 

 Tiddeman of the Geological Survey, and Mr. James Eccles of Black- 

 burn, have discovered abundance of encrinital remains in beds of 

 shale of this age ; the former on the banks of the Eibble, near 

 Eochester, and the latter near Eoach Bridge, on the river Darwen ; 

 and near the same place, some years ago, Mr. Binney mentions 

 meeting with Goniatites in a bed of black shale, which is now 



1 Transactions Manchester Geological Society, Vol. VII., p. 25. 



