218 



THE GEOLOGIST. 



foundation of cretaceous rocks containing Belemnites, Exogyrse, and 

 other fossils^ and that above them, with the occasional intervention of a 

 hgnite deposit, mentioned in the paper, on the authority of Mr. Vanux- 

 em, rest, first, the eocene Hmestone and marls, and secondly, the burr- 

 stone formation. The remarkable dissimilarity in the eocene limestone, 

 at different localities, may lead some observers to suspect that there 

 exists a considerable succession of subdivisions of the eocene period; and 

 Mr Lyell is willing to admit, that all the beds may not be precisely of 

 the same age, but he is inclined to ascribe the chief difference, first, to 

 the number of species procured at each place being small, and, therefore, 

 only a fraction of the entire Fauna of the period, so that variations in 

 each locality may have arisen from original geographical circumstances ; 

 and secondly, to there not having yet been formed any great eocene col- 

 lection from any part of the United States. Some fossils are conunon 

 to the limestone and the burr-stone formation, and he, therefore, con- 

 siders it as an upper eocene division, bearing, perhaps, the relation to 

 the calcareous beds, which the upper marine sands of the Paris basin 

 bear to the calcaire grassier, "With respect to beds of passage between 

 the cretaceous and secondary series, Mr. Lyell repeats the remark given 

 at the commencement of the paper ; but he said it would require a far 

 more extended investigation to enable a geologist to declare, whether 

 there may exist in the Southern States any such intermediate strata. 

 The generic affinity of the cretaceous fossils to those of Europe, is most 

 striking, and the author observed in Mr. Conrad's collection of Alabama 

 shells, a large Hippurite, an analogy pre^dously unnoticed. The propor- 

 tion of recent shells in the eocene strata of the United States, he says, 

 appears to be as small as in Europe, and the distinctiveness of the 

 eocene and miocene testacea, hitherto observed, to be as great. The 

 author also states as worthy of remark, that the recent shells in the 

 American miocene beds are not only in the same proportion to the 

 extinct as in the Suffolk crag, or the faluns of Touraine, but that they 

 also agree, in general, specifically with mollusca of the neighbouring sea, 

 in the same manner as the recent miocene species of Touraine agree with 

 species living on the western coast of France, or in the Mediterranean j 

 or as those of the crag agree with shells inhabiting the British seas. 



