1910.] OSI'RACODA I'llU.M TANriANYTKA. 755 



respect the South American form recently described l)v Dr. Daday 

 as Cypridinella ilosvagi. The structure of the le^s and the caudal 

 lobes is, however, very different, and on the whole in accord with 

 that found in the species of the present genus. 



Occurrence. — Some few female sjiecimens of this form, most of 

 them not in a good state of preservation, were found in a sample 

 from Victoria Nyanza (269), taken 25/4/05 at Bukoba (W. shore 

 of lake). 



General Remarks. 



The occurrence of Ostracoda in the samples taken by 

 Dr. Cunnington during the Tanganyika Expedition must on the 

 whole be regarded as a very unexpected circumstance, since these 

 samples, as a rule, were all taken at the very surface by the aid 

 of a line-meshed tow-net. None of the known freshwater 

 Ostracoda are, however, limnetic in habits, such as is the case with 

 many of the Ot)pepoda and Cladocera. They all ai-e true bottom 

 animals, though some of them are enabled, by the aid of the nata- 

 tory setiB attached to the antennae, to move freely in the water to 

 some extent. The occurrence of specimens of this group in the 

 samples may therefore be regarded as quite accidental, chiefly 

 caused by the circumstance that in some cases the samples have 

 been taken in quite shallow parts of the lakes, whereb}^ some 

 parcels of the bottom material have happened to be introduced 

 in the tow-net *. The great number of species determined is still 

 more perplexing and could easily lead to the wrong supposition 

 that the Ostracod material procured was a very large and exten- 

 sive one. This is, however, by no means the case. Tlie material 

 is in reality, as to quantity, very small, only one or two of the 

 species being represented by a tolerably great number of indi- 

 viduals, all the others only by quite solitary specimens. Although 

 the present account, therefore, in all pi-obability, only gives a 

 slight glimpse into the Ostracodous fauna of the three great 

 Centi'al African lakes, it will, I think, suffice to again emphasize 

 the peculiar faunistic character of Lake Tanganyika, as conq^ared 

 with the other two lakes. A glance at the annexed table of 

 distribution will show that the far greater number of species are 

 derived from that lake, and the contrast between Tanganyika and 

 the othei; two lakes is, in this case, even moi'e striking than in 

 the case of. the Copepoda, no less than 22 species occurring 

 in Tanganyika, whei'eas only thi'ee species are found in Lake 

 Nyasa and five species in Victoria Nyanza. It will, moreovei', be 

 seen that at the same time only a single species, S'tenoci/pris per- 

 armata, occurs in two of the lakes (Tanganyika and JSTj-asa) ; in all 

 other cases the species of the three lakes are different. Two 



* Di'. Cnnnington has recently called my attention to the fact that several of the 

 samples, and in particular those which turned out to be most productive in Ostra- 

 coda. were taken during the night ; and he has suggested that their occurrence iu 

 the surface-gatherings may more properly be explained by the very probable assump- 

 tion that freshwater Ostracoda, like many marine bottom-crustacea, rise to the 

 surface after dark. 



