566 DR. W. A. CUNJSIINGTON ON THE 



The existence of a large number of Ostracods which are 

 peculiar to Tanganyika is the principal feature displayed by the 

 list of species. Of the total number of forms on record, it will be 

 noted that Nyasa with 17 species does not fall far short of Tan- 

 ganyika with 22, while Victoria Nyanza is a long way behind 

 with only 7. This is probably due — at all events in part — to the 

 fact that Nyasa aiid its drainage area have been more thoroughly 

 investigated in this direction than Lake Victoria. It may further 

 be remarked that less than half the records from Nyasa are from 

 the actual waters of the lake itself, the remainder coming from 

 ponds and swamps etc. in the vicinity. Corresponding collec- 

 tions from the surrounding ponds, swamps, and rivers are wanting 

 in the case of both Victoi'ia and Tanganyika ; indeed, the v/hole 

 of the material collected in the thi-ee biggest lakes by the author's 

 expedition came only from the lakes themselves. Additional 

 records are therefore to be expected, particularly from Lakes 

 Victoria and Tanganyika Avhenever a more complete investigation 

 of the Eatomostraca becomes possible. 



While Nyasa is shown to contain nearly as many different 

 forms as Tanganyika, it Avill be seen that in the nature of these 

 forms the lakes differ profoundly. More than half the species 

 from Nyasa have also been obtained elsewhere, but of the 22 

 species from I'anganyika only two have so far been observed out- 

 side the confines of that lake, or to put it in another manner, 

 47 per cent, of the Nyasa forms are endemic in the lake, while 

 nearly 91 per cent, are endemic in the case of Tanganyika. 



Another feature of distribution which this table brings into 

 prominence is the association of certain groups of forms with 

 certain lakes. Only in three cases have species been recorded 

 from more than one lake — Stenocy2}ris perarmata from Tanganyika 

 and Nyasa, Zonocypris cosiata from Victoria and Nyasa, and 

 Paracypria ohtusa from Tanganyika and Albert. In every other 

 instance the species from the lakes differ from one another, and 

 appear to be either peculiar to or at least characteristic of the 

 lakes in which they are found. Without referring to the species 

 seriatim, it may be pointed out that the genera Stenocypris, 

 Potamocypris^ and Gypria seem to be associated in particular with 

 Nyasa, and Cypvipodsis with Tanganyika, while Paracypria, with 

 the exception of a single species, occurs only in Tanganyika 

 among the lakes. 



Apart from the forms peculiar to Tanganyika (which number 

 20 out of a total of 44 in the list of Ostracoda), it is to be observed 

 that 8 species are peculiar to Nyasa and 5 to Victoria Nyanza, 

 or 13 in all. It will thus be seen that when Tanganyika is 

 excluded, more endemic forms are known from the remaining 

 lakes than is the case among the Oopepoda. It is also singular 

 to note how restricted is the distribution of even the non- 

 endemic forms recorded, for only in a single case (that of Steno- 

 cypris malcolmsoni wliich is known from Asia and Australia) has 

 a species been obtained outside the continent of Africa with 

 Madagascar. 



To the genera Paracypria and Gypridopsis, which are so largely 



