214 FRESHWATER FAUNA 



large Paludina Neothauma points to this period. This 

 shell recalls the Paludinas, described by Neumayr, from 

 the Pontic beds, especially in the singular modifications 

 which it presents. According to Mr. Moore, its different 

 forms characterise particular bays, as though they were 

 the result of special local conditions; wiiile Neumayr's 

 forms succeed one another in different beds ; there is, 

 however, a possibility that Paludina will at any time 

 respond to a similar change of conditions by passing 



FIG. 79. Paludinas from the Laramie beds 

 and lake Tanganyika. The four figures 

 on the left, Neothauma Tanganyicense, 

 from Lake Tanganyika. After J. E. S. 

 Moore, (x f.) The two on the right, 

 Tulotoma Thompsons, White, from the 

 Laramie beds of North America. After 

 C. A. White. ( x f .) 



through a similar series of forms. This seems very likely, 

 and finds confirmation in the fact that a Paludina of the 

 Laramie beds presents similar varieties, i.e., conical and 

 keeled, to those of the Pontic beds and the Tanganyika 

 bays. 



The region in which the fauna took its origin is 

 unknown, it can scarcely have been Tanganyika. Mr. 

 Huddleston has summed up the geological evidence on 

 that point and given an adverse judgment, but it may 



