240 
THE TANGANYIKA PROBLEM. 
the inner face (Fig. 22), a very peculiar feature, and one 
which is only exemplified in the radula of Tympanotomus. 
The presence of this peculiarity, together with the general 
Fig. 23. — The nervous system of Bythoceras iricles- 
cens, as seen from above, c.g., Cerebral ganglion. 
sub. int. g., Subintestinal ganglion. 
character of the radula, should certainly be regarded as of 
weight in diagnosing the nearer affinities of this form. 
And, as we shall see in placing it along with Tympano - 
