TRANSLATIONS AND NOTICES 



OF 



GEOLOGICAL MEMOIRS. 



On the Lower Greensand and the Blackdown Fossils of 

 England. By M. E. Renevier. 



[Bulletin Soc. Vaudoise Sc. Nat. vol. v. p. 51-52, 1856.] 



In communicating the general results of his comparison of the lower 

 cretaceous fossils of England (large suites of which his late visit to 

 England had enabled him to study) with those of France and Switzer- 

 land, M. Renevier offered the following observations : — 



1st. Lower Greensand. — Palseontologically the Lower Greensand 

 does not represent the Neocomian of Switzerland, as most geologists 

 have thought ; but, on the contrary, exactly corresponds to the series 

 of Aptian beds which M. Renevier has recognized, at the Perte- 

 du-Rhone, between the upper Neocomian (Urgonian) and the Gault. 

 The lower strata of the Lower Greensand (Perna-beds and Crackers) 

 contain a fauna which is quite analogous to that of the Lower Ap- 

 tian (Rhodanian) of the Perte-du-Rhone, whilst the arenaceous series, 

 about 650 English feet thick, which occurs between the Crackers 

 and the Gault, evidently belongs to the Aptian proper. These two 

 faunas (Aptian and Rhodanian) are, however, much more closely 

 related in England than on the Continent ; hence the two series have 

 not hitherto been separated by the English geologists. Lastly, as in 

 Switzerland, the Aptian fauna is somewhat poor ; whilst the Rhoda- 

 nian fauna (Perna-beds and especially the Crackers) is on the con- 

 trary very rich. 



2nd. Blackdown. — The beautifully preserved fossils of Blackdown 

 have always drawn the attention of the palaeontologists of England to 

 this locality. The fauna has been sometimes referred to the Lower, 

 and sometimes to the Upper Greensand (Cenomanian) ; some, of 

 late, have referred it to the Gault ; and M. D'Archiac has regarded 

 it as representing all three of the above-cited series. 



M. Renevier was enabled to add a considerable number to the 

 known species of Blackdown fossils ; but does not offer a definite 

 opinion on the age of the deposit in question. Many of the species 

 are peculiar, but the majority belong also either to the Lower Green- 

 sand, the Gault, or the Upper Greensand. The Cephalopods are 

 few, both as specimens and species ; and though they are Gault forms, 

 yet the author thinks their evidence to be insufficient to decide the 

 question of the relative age of the deposit. Of the other classes, a 

 nearly equal number of the species are found also in the Upper 

 Greensand and the Gault ; and a somewhat less number occur in the 

 Lower Greensand. There is no doubt whatever of the mingling of these 

 species and of their occurrence in the same deposit. [T. R. J.] 



VOL. XII. — PART II, D 



