206 LIFE OF THE PLEISTOCENE 



In order that Ortmann's statement might be tested, casts were made of 

 several of the western species {recta, anodontoides, ligamentina, and alata as well 

 as the eastern nasuta and radiatus) and the fact became evident that Ortmann's 

 statement was abundantly borne out by the experiment. The casts bear little 

 or no resemblance to the species with which they are compared. Internal 

 casts are always uncertain objects to accurately identify and it will be difficult 

 to correlate the Fish-house material with modern forms. It seems evident, 

 however, that the fauna does not represent a recent migration from the west, 

 but an indigenous fauna, perhaps of long occupancy, modified by time and 

 related intimately to the present fauna of the Atlantic drainage. Many 

 of the figures published by Whitfield are strongly suggestive of such species as 

 complanatus quadrilaterus Lea, dariensis Lea, and jayensis Lea. All facts 

 at hand indicate that the fauna, while old, was not derived from western stock 

 (except remotely) but was a typical Atlantic coast fauna, living in waters 

 warmer than those of the present Delaware, and related intimately to the 

 species now living in the Carolinas and Georgia. 



Hi. Age of the Fish-house Clay 



Dr. Berry, 3 " who has studied the plant remains, places the Fish-house clay 

 flora and fauna in the late Pleistocene; he remarks that "in the judgment of 

 the writer the fossiliferous stratum at least is not older than the last interglacial 

 and the probability is strong though unverified, that it is post-glacial in age. " 



Recent geological works 31 place the Fish-house beds in the Pensauken stage 

 of the Columbia formation, which is about midway of the Pleistocene series. 

 In the Philadelphia Folio, 32 the following statements occur. 



"The Delaware River phase of the Pensauken is composed of debris which 

 is believed to have been brought down by streams from the north during one 

 of the early glacial epochs, an epoch which antedated the last glacial epoch 

 by a very long period of time. The streams, such as the Delaware, leading out 

 from the ice sheet and laden with debris which the ice had prepared, aggraded 

 their valleys, and the ice floating down the streams helped them to transport 

 the large pieces of rock, occasionly of bowlder size, which occur in the formation 

 of this region. The same agency — floating ice — helps to account for the un- 

 worn character of some of the coarse material of the formation, and at the same 

 time affords a rational explanation of the presence so far from its source of such 

 soft materials as the friable Newark shale and sandstone. It is not believed 

 that rivers, unaided by floating ice, could have carried them so far, and it is 

 still more incredible that they could have been transported from their original 

 position by waves. Furthermore, a single well-glaciated stone has been found 



'« Torreya, X, pp. 260-262, 1910. 



31 Chamberlin and Salisbury, Geology, III, p. 451. 



» U. S. Geol. Surv., Atlas, No. 162, p. 14. 



