FAUNA OF TPIE AFRICAN LAKES. 547 



detailed examination. Among the Viviparidfe, Viviparus itself 

 is represented in 'I'anganyika only by two (one doubtful) endemic 

 forms. In Lake Victoria there is a sei'ies of 5 forms, 3 of which 

 are peculiar to its waters. It is noteworthy that the widely dis- 

 tributed species V. ruhicundus and V. imicolor have not been 

 obtained from Tanganj'ika. The genera JVeothatuna nnd J^ridouxia 

 are of more interest, since they are entirely confined to Tan- 

 ganyika,. The latter genus has been regarded as exhibiting a 

 thnlassoid facies. Each is represented by only a single species. 



The family Ampullariidas contains representatives of the well- 

 known genera Ampidlaria and Lanistes in addition to the 

 thalassoid genus Leroya from Tanganyika. Only Victoria 

 Nyanza and Tanganyika possess endemic forms of the two first- 

 mentioned genera, the remaining species — especially Amptdla7-ia 

 ovata — having a wider disti'ibiition. Lake Victoria will be seen 

 to have five species of Ampallaria, Nyasa a similar number of 

 Lanistes. The latter genus has not been recorded from the 

 smaller lakes. 



A larger number of genera, several of great interest, are asso- 

 ciated in the family Hydrobiidse. Bithynia* alone among the 

 genera enumerated is found outside the confines of Tanganyika, 

 but the species on record from the lakes have not been found in 

 other parts of the continent. Of the thalassoid types, Sianleya 

 is represented by 3 species and Syrnnlopsis by 2. Chytra and 

 Limnotrockus, as the name of the latter indicates, are forms in 

 which the shell is suggestive of the marine genus Troclius. 



The genera belonging to the family TiaridEe(formerly Melaniidse) 

 form by far the largest assemblage in the list under consideration. 

 Thirteen genera are represented, but here again only one of them, 

 the type-genu8 Tiara itself (perhaps better known as Melania) is 

 of wide distribution, the remainder being thalassoid forms found 

 only in Tanganyika. Tlie latter lake contains three species of 

 Tiara, two of which are endemic ; Albert Nyanza contains one 

 endemic as well as one non-endemic species, while ISTyasa contains 

 a remarkable series of nine difi*erent types, seven of which are 

 endemic. It is interesting to note that Tiara tuiercidata, which 

 lias a wide range in Africa and extends into India and the Malay 

 Archipelago, is the only one of the 133 species enumerated Avhich 

 occurs in all the lakes included in this survey. There is little 

 need for comment on the remaining genera in this family. They 

 contain the greater number of those types of marine a,spect which 

 are so remarkable a, feature of the Gasteropod fauna of Tangan- 

 yika. ( 'ertain of the genera are, however, represented by quite 

 a number of species, notably Edgaria by 9 species and Giraudia 

 and Lavigeria each by 8. 



Under the family name of Tiphobiidse have been associated the 



* A species of Bitliynia is stated by Moore (137, p. 129) to occur in Lake Kivu. 

 I believe no specimens have ever reached tliis country, and in view of the negative 

 evidence which the visit of the German expedition to the lake affords, I regard the 

 record as of doubtful value and have intentionallj'' omitted it. 



