THE TANGANYIKA PROBLEM. 
241 
tomus , it is certainly in accord with the rest of the animal’s 
morphological peculiarities. 
The oesophagus and salivary glands are in all ways 
similar to those of Ty phobia * but these characters are 
common to so many different kinds of gastropods that they 
are of little value from a special morphological point of 
view. 
The stomach has two chambers, the anterior of which con- 
tains a style. The intestine is simple, and in Tanganyicia 
takes the course represented in Fig. 32. The rectum 
is not dilated, nor beset with any accessory gland. The 
bile ducts seem to open by two very small apertures upon 
the base of the posterior stomachic chamber. Stomachic 
valves are feebly, if at all, developed. The liver is large, 
and occupies much the same position as Nassopsis (see 
below). The excretory organ occupies a place in front of 
and above the heart and opens by a minute pore at the 
extreme upper end of the mantle cavity, Fig. 29. 
The heart has the usual taenioglossate characters, con- 
sisting of an auricle, ventricle, and aortic trunk ; but the 
last structure is much less developed in Bythoceras than in 
many forms — as, for example, in the genus Typhobia. 
The nervous system in Bythoceras (Fig. 23) is very 
interesting, since it is absolutely unlike that possessed by 
the genus Nassopsis, and closely simulates the type described 
by Bouvierf as typical of the genus Cerithium. It also 
strongly resembles that of the genus Tanganyicia. Viewed 
from above, Fig. 23, the cerebral ganglia are seen to be 
closely fused together, while the left pleural and sub-in- 
testinal ganglion, as in Cerithium , form a single massive 
trunk, which at its hinder extremity gives rise to the sub- 
* Loc. cit. , “ Quart. Journ. Micr. Sci.,” Vol. 41, 1898, p. 190. 
t “Ann. Dis. Sci. Nat.,” 1887, PP- 131-135, pi. vii. 
l6 
