226 



THE TANGANYIKA PROBLEM. 



the blood from the gill, and a muscular ventricle, which 

 is connected with a typical posterior and anterior aortic 

 trunk. 



In Ty phobia, the nerves are arranged on the plan pre- 

 sented in such well-known types as CeritJiium and Strombus, 

 both the cerebral and pleural ganglia are all above the 

 oesophagus, and are closely applied together (Fig. 3). 

 The cerebro-pedal and pleuro-pedal cords are of medium 

 length. The pedal ganglia are rather long and cord- 



Fig. 7. — Part of the mantle cavity of Typliobia 

 horei, showing the rectum {R) and the genital 

 duct in the male (g.a. ). 



like, and are connected together by some ladder-like 

 connections. The otocysts (Fig. 6) are large, and 

 the otocyst nerves very short ; the otocysts being, in 

 consequence, very high up in the head. The otoliths 

 are numerous and each shaped like a barrel. In 

 Typhobia, as in Cerithium and Vermetus, the subin- 

 testinal ganglion has become approximated to the left 

 pleural, while the supra-intestinal ganglion and its cord 

 spring from the right pleural, both retaining their usual 



