PREGLACIAL CONDITIONS AND LIFE 205 



Unio nasutoides Lea nasutus Say Atlantic drainage 



" cariosoides Lea cariosus Say " 



" roanokoides Lea roanokensis Lea 



Vertebrata (Pisces) 

 Fish scales of undetermined species. 



Mammalia 

 Equus complicatus Leidy. 



It will be noted that of the twelve species of mollusks listed, only four re- 

 semble the species now living in the Delaware River. 28 Of the balance three 

 are compared with species found in the St. Lawrence and Mississippi River 

 drainages, while four of the compared species are confined exclusively to the 

 Mississippi River and its tributaries. It will also be noted that there is a total 

 absence of the heavy, rounded or tuberculate naiads of the Mississippi and 

 Ohio rivers and this feature of the fauna is believed by Pilsbry to indicate a 

 migration via the Great Lakes region, and thru some river systems in New York, 

 where head waters were near the head waters of the ancient Delaware River. 

 Pilsbry further states that the fauna is "either interglacial or preglacial, 

 and probably the latter. " The fact that there is a total lack of trans-Alleghenian 

 species in the present molluscan fauna of the Delaware River points to the 

 great antiquity of the Fish-house fauna, and the presence of the river type of 

 mussels indicates a migration by a river system, which could only have been 

 preglacial as it is believed that subsequent to the Kansan Glacial Epoch, the 

 Great Lakes region has contained a lake rather than a river system. The 

 abundance of the fauna taken in connection with their "divergence from the 

 most alhed living forms, point to preglacial rather than interglacial conditions." 



Ortmann 29 does not agree with Pilsbry, Lea, and Whitfield in the relation- 

 ship assigned to these mollusks. He says "But for the present time these fos- 

 sils are absolutely useless, because western affinities have been maintained 

 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.' ' 



M The four species are complanatus, nasutus, radialus, cariosus. 

 » Proc. Amer. Phil. Soc, LII, p. 280, 1913. 



V 



