234 THE TANGANYIKA PROBLEM. 



which corresponds in position and appearance to that 

 encountered in the same place in Xenophora. 

 The animal does not appear to be viviparous. 



limnotrochus, smith. limnotrochus thomsoni 



(fig. 17). 



As I have previously stated, the shell of this animal 

 (Fig. 17) was originally described by Smith. During the 

 first Tanganyika expedition, only one badly preserved 



Fig. 18. — The lingual dentition of Limnotrochus thomsoiii (X 150). 



specimen was obtained ; but during the second, five 

 specimens in good condition were dredged, not, however, 

 without much trouble and in the southern portion of the 

 lake. As in the case of Chytra, the anatomical material 

 obtained was examined by Miss Digby, from whose 

 results I have condensed the following description. 



The tentacles are shorter than in Chytra, and the snout 

 and body more pigmented. The snout is short, and the 

 buccal mass much farther back than in Chytra. The oper- 

 culum is curiously oblong in shape, litterinoid and concave. 



