chap. xiv. Neocomian Fossils. 5 1 1 



■ of shells, that I have no doubt they have fallen from it. 

 The yellow magnesian limestone of bed No. 10, which 

 also includes traces of shells, has a different appearance. 

 These fossils (as named by M. d'Orbigny) consist of — 



Gryphasa, near to G. Couloni (Neocomian formation). 

 Area, perhaps A. Gabrielis, d'Orbig. ' Pal. Franc.' (Neocomian for- 

 mation). 



Mr. Pentland made a collection of shells from this 



same spot, and Von Buch l considers them as consisting 



of— 



Trigonia, resembling in form T. costata. 



Pholadomya, like one found by M. Dufresnoy near Alencon. 



Isocardiaexcentrica, Voltz., identical with that from the Jura. 



Two of these shells, namely, the Gryphaea and 

 Trigonia, appear to be identical with species collected 

 by Meyen and myself on the Peuquenes range ; and in 

 the opinion of Yon Buch and M. d'Orbigny, the two 

 formations belong to the same age. I must here add, 

 that Professor E. Forbes, who has examined my speci- 

 mens from this place and from the Peuquenes range, 

 has likewise a strong impression that they indicate the 

 Cretaceous period, and probably an early epoch in it : 

 so that all the palaeontologists who have seen these 

 fossils nearly coincide in opinion regarding their age. 

 The limestone, however, with these fossils here lies at 

 the very base of the formation, just above the porphyritic 

 conglomerate, and certainly several thousand feet lower 

 in the series, than the equivalent, fossiliferous, black, 

 shaly rocks high up on the Peuquenes range. 



It is well worthy of remark that these shells, or at 

 least those of which I saw impressions in the limestone 

 (bed No. 3), must have been covered up, on the least 

 computation, by 4,000 feet of strata : now we know 



1 ' Descript. Phys. des lies Can.' p. 472. 



