COMPARISON OF SHREWSBURY AND MANCHESTER DEPOSITS. 



89 



species occur in the beds of mottled marls above the limestones, in the black bass or shale above 

 the main limestone, and in the shale beneath all the calcareous bands. Another bivalve found 

 in the black bass above the limestone is probably a Cyclas, and a singular bivalvular body, found in 

 the shale by Mr. Williamson, I would describe as most resembling Aptychus, being equivalved, with 

 a straight hinge the breadth of the shell, the anterior side rounded, the posterior truncate, two 

 diverging ridges from the beak, about twelve crenate furrows parallel to the margin, and all alike, 

 colour fine brown, appearance like a fish scale, the inside nearly smooth. Of Crustacea, I found 

 in the black bass one Cypris, having a very glossy shell of elliptical shape, and in prodigious 

 abundance, mixed with fish scales. Another species of Cypris I discovered in the roof of the yard 

 coal (see section, p. 870? probably the same as one I formerly found in the lower coal strata near 

 Halifax, and which also occurs in the coal-measures of the Tyne. 



"Of vertebrated fossils the black bass contains abundance of fragments, chiefly belonging to Pa- 

 Iceoniscus Freieslebeni} of the Magnesian Limestone , and another species with plain scales, such as 

 occurs in foreign coal tracts. I also detected large scales of the beautiful large species of fish formerly 

 found in the coal measures near Leeds, and which is deposited in the museum of that town, and I was 

 still more gratified to detect in the main bed of limestone a considerable number of bones, which re- 

 minded me of reptile structure, together with portions of skin, continuous, beautifully striated, and 

 shagreened. My impression, that these were portions of a reptile, was strengthened by finding 

 large bones, possibly of the head, pitted and roughened very differently from the surface of the bones 

 found at Burdie House near Edinburgh, and at Leeds. Mr. Mellor has since found a jaw with 

 teeth very similar to Holoptychus Hibberti (Agass.). Mr. Francis Loomy discovered a tooth, pro- 

 bably of Ctenodus; and a splendid specimen of this genus perfectly identical with the C. Mur- 

 chisonii (Agass.) of Le Botwood, has been placed in the Manchester Museum by Mr. Miller. 



The upper carbonaceous zone of Lancashire is thus identified by mineral characters and 

 by organic remains with the Shrewsbury coal-field, from which, however, it differs in 

 exhibiting a much greater development of limestone ; and with this increase of calcareous 

 matter, we perceive a corresponding increase in the number and variety of the remains 

 of animal life, particularly in the testaceous Mollusca, whose existence could not have been 

 prolonged without an adequate supply of carbonate of lime. Similar analogies of in- 

 creased numbers of fossil shells, where calcareous rocks prevail, will be pointed out in 

 the course of this work in other strata of much higher antiquity. It is further highly 

 interesting to observe in these rich fossiliferous beds of Manchester, the occurrence of 

 the Palceoniscus Freieslebeni?, a fish eminently characteristic of the Magnesian Lime- 

 stone, associated with some peculiar animal remains, and with many plants and other 

 fossils common to the ordinary coal measures, an intermixture which affords zoological 

 proofs, that the zone in question is made up of transition strata, connecting the New 

 Red and Carboniferous Systems. At the same time, (if the species be correctly deter- 

 mined) \ this discovery tends to modify one of the strongly defined stratigraphical cha- 

 racters assigned to fossil fishes by the researches of M. Agassiz ; for whilst occasionally 



! I have requested Professor Phillips to send the specimens to London, and the result of their examination 

 will be announced in the Appendix. 



