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 Cerithium and Strombus, 
both the cerebral and pleural ganglia are all above the 
oesophagus, and are closely applied together (big. 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 Typhobia 
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 
