456 FOSSIL INVERTEBRATED ANIMALS. 



swallows. Now, as we are certain that a very great number 

 of genera found in the fossil state exist no longer, we may 

 conjecture that, after their disappearance, some changes must 

 have taken place in the situation of the beings then existing — 

 the nature of such changes we cannot appreciate, but we ob- 

 serve that the number of genera has augmented in the coarse 

 limestone. 



It is stated that in this stratum, at Grignon, more genera 

 and species are found than could be found on any of the 

 French coasts. This M. de France believes to be the case, in 

 consequence of the temperate character of the actual climate 

 of France. But he does not hesitate to believe, that between 

 the tropics, where the seas contain a much greater quantity of 

 mollusca, the coasts or bottom of those seas abound as much 

 in debris of testaceous marine bodies as the stratum of Gri- 

 gnon, and that it cannot be doubted that this stratum was 

 formed under a climate analogous to that of the tropics. The 

 nautili, and many other fossil genera of this locality, not found 

 living except in the hot climate, establish the certainty of this 

 point. 



There does not appear to be any remarkable difference be- 

 tween the fossils of Europe and those of America. At the 

 mouth of the Alleghany river, and on the banks of the Mo- 

 hauk river, near Utica, in the state of New York, are found 

 trilobites, encrinites, terebratulites, and other shells, which 

 must have come from very ancient strata, and in which the testa 

 has disappeared. A specimen of sandstone from the summit of 

 the Alleghany mountains was found filled with internal moulds 

 of debris of the stems of encrinites. Beyond the rivers of Ge- 

 nesee, in proceeding to the falls of Niagara, the internal sili- 

 ceous moulds of shells are found, both univalve and bivalve, 

 which may be suspected to belong to the coarse or crag-lime- 

 stone. Specimens have been seen from Virginia, which ap- 

 peared evidently to have been derived from a bed of this last- 

 mentioned formation. They contained petunculi, arcae, mac- 



