THE TANGANYIKA PROBLEM. 



345 



Purpurina has been given, and which have generally 

 been considered as belonging to the Rhipidoglossa. The 

 specimens of Purpurina bellona which I examined in 

 Mr. Hudleston's collection, and a fine example of which is 

 represented below, are closely similar to the living shells 



Paramelania damoni, upper figure, compared with Purpurina bellona, lower, 

 a marine Jurassic fossil. 



of Paramelania damoni of Tanganyika, and the living 

 form has been represented side by side with the Jurassic 

 fossil in the above figure. In this, as in other cases, I 

 consulted Mr. Edgar Smith with respect to the value of 

 such a comparison in a conchological sense, and he assured 

 me that, even within a specific range, there is no valid 

 conchological distinction between the shell of the living 



