316 J. E. S. MOORE. 



as amended by him the diagnosis runs — " Shell turbinate, 

 more rarely trochoid, rather thin, imperforate or nearly so; 

 subelongate, frequently turreted ; sutural space wide; orna- 

 mented with spiral bands, usually spinulous or nodular, some 

 of which are prominent. The interspaces are finely striated, 

 the striae being slightly oblique to the axis; sometimes these 

 fine lines are strong enough to represent fine axial ribs. Base 

 rounded, spirally ribbed, and marked by fine radial striae ; aper- 

 ture suboval, but varying according to age, in the adult more 

 or less rounded, so as to become suboval or subcircular ; there 

 is usually a considerable deposit of callus; outer lip thin, often 

 crenulate." 



This description would certainly answer for that of one of 

 the new types which I found in Tanganyika, and for which 1 

 have proposed the generic name Bath an alia (fig. 3), for 

 although the Jurassic genus Amberlya shows a considerable 

 range of specific variation, all its species have essentially the 

 same characteristics as the two represented in fig. 3a, upper 

 and lower. The thin shell, the absence of all trace of epi- 

 dermis, and the character of the whorls, as well as the sculpture 

 and the character of the mouth, are all essentially the same in 

 Bathanalia as they are in Amberlya; the only point in 

 which they differ is in the columella, that of Bathanalia 

 being generally open, while that of Amberlya is always closed. 

 I have, however, consulted Mr. Edgar Smith and others about 

 this, and he assures me that such differences cannot be upheld 

 as generically distinctive, more especially as the amount of 

 umbilical opening in Bathanalia varies a good deal in extent 

 from shell to shell. We may, therefore, conclude that con- 

 chologically Bathanalia and Amberlya are the same. 



The next example of the close similarity existing between 

 the living shells in Tanganyika and the marine Jurassic types 

 is that afforded by the Limnotrochus Thompsoni of the 

 one and certain so-called Littorinas of the other. In fig. 5 

 are represented two views of L. Thompsoni, while in fig. 5a 

 are given similar views of the Jurassic species Littorina 

 sulcata. 



