2 3 6 
THE TANGANYIKA PROBLEM. 
the nerves, the pleural ganglia extending posteriorly and 
ventrally to such a degree that they are almost fused up 
with the pedal ganglia. In consequence of this, the cero- 
pedal cords are relatively very much longer than the reduced 
cerebro-pleural. The otocysts are in the usual position 
behind and above the pedal ganglia ; and the otoliths are 
numerous and sharply rectangular. 
The radula of Limnotrochus (Fig. 18) is distinctive of 
the genus, its most striking feature being the blunt pro- 
tuberance seen on the outer edge of each lateral tooth. 
The mouth leads into a very short buccal mass, into the 
posterior portion of which there open two very diminutive 
and simply saccular salivary glands. The oesophagus is 
straight, except for one sharp bend just before it enters 
the stomach. 
Like that of Chytra the stomach of Limnotrochus is 
divided into two chambers, the anterior one being con- 
stricted off from the stomach proper by a thickened and 
nearly circular annulus. The anterior chamber contains 
a crystalline style ; the walls of the anterior stomachic 
chamber, or style sac, are thick, while those of the posterior 
chamber are, relatively, thin. In the latter, in the stomach 
proper, there is a conspicuous median fold, which as in 
Trochus and Chytra becomes duplicated, surrounds the 
aperture of a bile duct and then passes backward into a 
very well developed spiral caecum. 
The intestine leaves the stomach on the right, and after 
characteristically twisting twice round the style sac, passes 
directly away through the mantle cavity to the anus. The 
kidney is large, lying below and around the heart, and 
opens by a minute aperture at the upper angle of the 
mantle cavity, the heart itself having the normal Taenio- 
glossate characters. 
