380 ORTMANN— THE ALLEGHENIAN DIVIDE. [April 1 8, 



help of the modern, artificial canals. But, of course, it is difficult 

 to decide positively whether canals have played a necessary part in 

 this dispersal. This question should be investigated in connection 

 with the other western forms, which have taken the route of the 

 Erie canal ; but this is not our present object. 



The above studies would be more complete if the conclusions 

 were supported by paleontological evidence; if we had fossil rem- 

 nants of N a jades or other aquatic creatures which would give us 

 an idea as to the faunas of the two watersheds in the past, chiefly 

 during Tertiary times. It is very much to be regretted that prac- 

 tically nothing is known in this line. 



There is indeed a famous locality, Fish House, Camden Co., 

 New Jersey, opposite Philadelphia, which has yielded fossil Najades, 

 probably belonging to the Glacial time. These shells have been de- 

 scribed and discussed by Lea and chiefly by Whitfield (Mon. U. S. 

 Geol. Surv., 9, 1885), and their geological age has been ascertained 

 by Woolman (Ann. Rep. Geol. Surv. N. J. (for 1896), 1897, p. 

 201 ff.), Pilsbry (Pr. Ac. Philad., 1896, p. 567) and Simpson (Pr. 

 U. S. Mus., 1895, p. 338). But for the present time these fossils 

 are absolutely useless, because western affinities have been main- 

 tained for these species, which surely do not exist. The species 

 have been identified mainly from casts, and Lea as well as Whitfield 

 have indicated, by the names given to them, their supposed affinities 

 to western species. I have taken the trouble of making plaster 

 casts of the inside of specimens of the living species with which they 

 have been correlated, and practically in all cases it became evident 

 at a glance that there was no similarity at all. 



But this should be the subject of a special paper. It suffices here 

 to make the statement, first, that the number of species described 

 from this deposit (about a dozen) should be reduced to not more 

 than three or four, and second, that there is not a single one which 

 has distinct and unmistakable affinities to any typical western species. 



