LAKE TANGANYIKA — AN OLD JURASSIC SEA. 



307 



of two distinct types, one of which, represented by L. 

 Thompsoni, is closely similar to Bathanalia; while the other, 

 represented by the unique L. Kirkii, is the only fresh-water 

 Xenophora (Onustus) at present known. 



5. That in the Pararaelanian group, composed of the genera 

 Paramelania, Nassopsis, and Bythoceras, we have forms 



have used the family name Purpuriuidae to include the genera Parame- 

 lania, Nasopsis, and Bythoceras, and the new generic name Chytra for 

 the old generic name of Limnotrochus, in the case of L. Kirkii. 



Conchological Classification 

 according to M. Fischer. 



Fam. — Melaniidse. 

 Genus. — Typhobia (Smith). 



T. Horei, Smith. 

 Genus. — Paramelania (Smith). 



P. Damoni, Smith. 



M, nassa, S. P. Woodw. 

 F a m. — Hy drobiidse. 

 Genus. — ? ? Syrnolopsis (Smith). 



S. lacustris, Smith. 

 Genus. — Spekia (Bourguignat). 



S. zonata, S. P. Woodw. 

 Genus. — Tanganyicia (Crosse). 



T. rufofilosa, S. P. AVoodw. 

 Genus. — Limnotrochus (Smith). 



L. Thomsoni, Smith. 



L. Kirkii, Smith. 



Redetermination from the 

 Characters of the Animals 

 themselves. 



Fam. — Typhobiidse (Moore). 

 Genus. — Typhobia. 



T. Horei, Smith. 

 Genus. — Bathanalia (Moore). 



B. Howesii, Moore. 

 Genus. — Limnotrochus (Smith). 



L. Thomsoni, Smith. 

 F a m. — Planaxidae. 

 Genus. — Tanganyicia (Crosse). 



T. rufofilosa, S. P. Woodw. 

 Fam. — Xenophoridee. 

 Genus. — Chytra (Moore). 



C. Kirkii, Smith. 

 F a m. — Purpurinidse. 



Genus. — Paramelania (Smith) 

 = Purpuriua (Hudl.). 

 P. Damoni, Smith. 

 P. crassigranulata, Smith. 

 Genus. — Nassopsis (Smith). 



N. nassa, S. P. Woodw. 

 Genus. — Bythoceras (Moore). 

 B. iridesceus, Moore. 

 Fam. — Naticidae. 

 Genus. — Spekia (Bourguignat). 

 S. zonata. 



In the above list I have placed the genus Chytra among the Xenopho- 

 ridae on account of its conchological similarity to numerous fossils which are 

 referred to this group. 



The notes of interrogation in the older list are those of M. Fischer. 



