232 



THE TANGANYIKA PROBLEM. 



valvular fold which becomes doubled near the aperture of 

 a bile duct, and then passes, as in Trochus, into a small, but 

 quite well developed, spiral caecum. Except for the presence 

 of the anterior chamber, which appears to be absent in the 

 genus Trochus, Chytra possesses a stomachic apparatus 



Fig. 15. — The nervous system of Chytra kirkii dissected from above. (From a 

 drawing by Miss Digby.) 



strictly comparable to that in the majority of the Rhipido- 

 glossa, including Pleurotomaria itself. 



The intestine leaves the stomach on the left, and after a 

 characteristic double twist, enlarges into the rectum. This 

 enlarged rectum is filled with complex glandular folds, but 

 narrows again before it opens at the anus, which has a 

 distinctly modified rim. 



The heart has the typical Taenioglossate characters, and 



