THE TANGANYIKA PROBLEM. 
2 33 
the gill and the gill leaves are identical with those of 
Aporrhais. The kidney lies around and below the heart, 
Fig. 1 6. — Operculum of Chytra kirkii. 
and opens, as in Aporrhais and Capulus , at the extreme 
upper end of the mantle cavity. The liver is large, occupy- 
Fig. 17. — Two views of the shell of Limnotrochus thomsoni (+ §). 
ing much of the upper part of the visceral hump, and on its 
outer surface there is lodged the flattened foliated mass of 
Fig. 1 8a. — Operculum of Limnotrochus thomsoni. 
the genital gland. The duct of this leads without much 
coiling into the mantle cavity, where, in the female, it 
enlarges, and is related to a curious glandular (?) organ 
