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, 





fc? 



z* #*&■<■ 



Fig. 16. — 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 (+ J)- 



ing much of the upper part of the visceral hump, and on its 

 outer surface there is lodged the flattened foliated mass of 



Fig. i8a. — 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 



