698 Professor Sedgwick and R. I. Murchison, Esq., on the 



Coupling- this account with the near resemblance of some of the South 

 Devon shells to known fossils of the mountain limestone, we at once establish 

 our main position, that the South Devon fossils are of an intermediate type 

 between those of the Silurian and carboniferous systems. It also follows 

 from the same evidence, that the North and South Devon corals belong to 

 rocks which are very nearly on the same parallel, as the most abundant corals 

 of the lower North Devon groups agree specifically with the most abundant 

 corals of the Plymouth and Tor Bay limestones. 



As far as regards the fossil shells, we must refer to the accompanying lists. 

 We may however remark, in our present summary, that we have shells in the 

 Plymouth limestone which make a near approach to Terebratula Wilsoni, 

 Airypa orbicularis, Orthis depressa, PHeopsis vetustatis, Nerita Haliotis, 

 and Orthoceratites circularis, of the upper Silurian rocks. Most of them, 

 however, when closely examined, present some points, we think, of specific 

 difference. On the other hand, this limestone contains some genera and 

 species very nearly resembling certain fossils (such as Pecten dissimilis (Phil- 

 lips), P. plicatus (Sowerby), P. arenosus (Phillips), Terebratula acuminata 

 (Sowerby), Producta analo^a (Phillips), &c. &c.) of the carboniferous lime- 

 stone. Lastly, we may remark, that many species in the Plymouth limestone 

 (and those, we believe, the most abundant) are quite distinct from the fossils 

 both of the carboniferous and Silurian systems ; among which we may point 

 out a very large Atrypa, Buccinum spinosum, a large Natica, and several 

 small univalves. (See the Lists.) 



We have many fossils from the neighbourhood of Newton Bushel, chiefly, 

 however, in the form of sihceous casts : we forbear, however, to dwell on 

 them, as Professor Phillips and Mr. Austen are, we believe, both engaged in 

 their description. Some of them agree specifically with shells of the Ply- 

 mouth limestone; others are new; several of them nearly approach the forms 

 of the mountain limestone (as we learn from the description of Mr. Austen, 

 and the recently published " Report" of Mr. De la Beche) ; and the corals, at 

 least the most abundant species, agree with corals of the Plymouth and Ilfra- 

 combe limestones. 



Such is a brief summary of the results arising out of an examination of the 

 South Devon fossils ; and the conclusion to which they point appears to us 

 absolutely inevitable, viz. that the South Devon series is intermediate between 

 the carboniferous and Silurian systems, and consequently on the parallel of 

 the old red sandstone. 



After the details of our previous communication, it is evident that all the 

 calcareous slates on the south-eastern side of Cornwall are of the age of the 

 owest group of the South Devon section, and therefore probably in the lower 



