244 



THE TANGANYIKA PROBLEM. 



B. MINOR, MOORE (FIG. 24). 



During the second Tanganyika expedition a new species 

 of Bythoceras was obtained, which has not yet been figured 

 or described, and to which I have given the above distinc- 

 tive name (Fig. 24). This form is somewhat smaller 

 than B. howesii and possesses a less marked epidermis. 

 In other respects it does not differ from the original type of 

 the genus. 



Fig. 26. — The lingual dentition of Paramelania crassigramilata. 



PARAMELANTA, SMITH. P. DAMONI (FIG. 2j). 



In its general structural peculiarities, the genus Para- 

 melania closely resembles Ty phobia and the preceding 

 group of forms, but it differs from them all in several 

 marked peculiarities. Thus, the shell (Fig. 27) is highly 

 characteristic, and in form and sculpture indistinguishable 

 from the old marine Jurassic form Purpurina bellona ; 

 it has also generally more apparent epidermis, though the 

 living shells may at the same time be quite without. 



In the mantle cavity the parts are arranged almost 



