242 



and the Devonian he divided into several faunae, according to 

 Prof. Hall, many of which he had satisfied himself from examina- 

 tion of their fossils were distinct ; these answered, as a general 

 rule, to the subdivisions or groups adopted by Profs. H. D. and 

 W. B. Rogers in their " Geology of Pennsylvania and Virginia ; " 

 the faunie of the Devonian he had not as yet been able to de- 

 termine ; he would characterize the primary up to the carbon- 

 iferous as being composed of exclusively marine faun«, as the 

 age of fishes. 



In the carboniferous age marshy land appeared, the beginning 

 of continental lands with inland waters. In the tertiary, accord- 

 ing to Mr. Lyell, 4 or 5 per cent, of the eocene species pass on to 

 the present period, 19 per cent, in the miocene, and about one 

 half in the pliocene ; this he regarded as an error which would 

 not have been committed with a sound zoologist by his side. He 

 instanced Rostellaria jissurella, which had been considered identi- 

 cal in several formations, as being easily recognized to embrace 

 distinct species on actual comparison of the specimens. He ob- 

 jected to Deshayes's principle of requiring equal and great differ- 

 ences in the determination of species, as what would constitute a 

 specific difference in one case might be far greater than that re- 

 quired in another. The mastodon and Elephas primigenius are 

 acknowledged to be extinct, and he saw no reason why other 

 classes in the animal kingdom should not be exterminated by the 

 same causes ; he was convinced that careful examination would 

 show that the lowest mollusks in the tertiary beds are as different 

 from the present as are the larger animals. 



Prof. Rogers replied that the entire severance of these faunae 

 must be demonstrated, before such a line of reasoning can be em- 

 ployed against the theory of Darwin ; if such a distinction be true, 

 we must abandon nearly all the hitherto accepted specific deter- 

 minations of other accomplished zoologists, most of whom main- 

 tain that animal forms do pass from one stratum to another. The 

 division lines, moreover, are essentially local ; the number of spe- 

 cies said to pass from one formation to another may be so great 

 in some localities as entirely to obliterate divisions which in other 

 and not very remote places are marked by very sharp transitions. 



Thus in New York, out of more than seventy forms found in 



