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 
