FAUNA OF THE AFRICAN LAKES. 



567 



represented in Tanganyika, it is necessary to call special attention 

 on account of their remarkable nature. Of the former genus, no 

 fewer than twelve difierent species have been described from that 

 lake, eleven of which are peculiar to it, and they all, as Sars points 

 out (152, p. 756), exhibit striking features of specialisation. 

 It is also a remarkable coincidence — if it is only that — that the 

 type species of Paracypria was obtained from the same brackish 

 lagoon on the Chatham Islands as was the type of the Copepod 

 genus Schizopera, which is likewise very characteristic of Tan- 

 ganyika among the lakes. The case of Cypridopsis is perhaps 

 more significant still, since of the ten species obtained by the 

 Third Tanganyika Expedition two only display all the features 

 characteristic of the genus, and these are the two forms taken 

 respectively in Lakes Nyasa and Yictoiaa. The other eight types, 

 which are confined to Tanganyika, exhibit certain divei'gences 

 which suggest that they might more suitably be removed to a new 

 genus which would then l)e endemic in the lake (152, p. 757). 



It is quite clear that in the case of this group also, Tanganyika 

 contains an unusually large number of forms, an exceptional 

 proportion of which are peculiar to the lake, and that of these 

 peculiar forms many show undoubted signs of specialisation. 



Cladocera . 



The outstanding fact concerning the Cladocera is the absence 

 of any representatives from the plankton of Tanganyika, and 

 also apparently of Kivu, which is in direct communication with 

 it. Thus the survey of this group of organisms resolves itself 

 into a comparison of the records from the remaining lakes, and 

 this, it is not surprising to find, lacks the interest which the 

 inclusion of species fi-om Tanganyika usually afii'ords. 



Tahle of Distribution of Cladocera t. 



Name of Species. ^^^^^^^"^^^ Nyasa. ^^^'^^'^ ^'^^''"'^ Other parts of 



^ JNyatiza. ^ Nyanza. Nyanza. the world. 



Family Sidid^. 



Parasida szalayi ... P ... ... Asia. 



Diaphanosoma excismn ... P P ... P E. Africa, Australia. 



Family Daphnid.^. 



Daphnia kirimensis .. ... ... E 



lous-ispina P ... ... ... Cosmopolitan. 



„ hyalina P ... ... ... Cosmopolitan. 



lumholtzi P P ... ... Palestine, Australia. 



„ monacha ... E 



Hyalodaphnia barbata P ... ... ... E.Africa. 



Cerioda})hnia bicuspidata... P ... ... P 



cornuta P P§ ... ... Asia, Australia, S. Americ; 



5, dubia P .. ... ... Sumatra. 



„ rigaudi P P§ ... P Almost cosmopolitan. 



t For further particulars consult especially Daday (76, p. 120). Additional 

 records for Lake Victoria are given bv Delachaux (77) and for the smaller lakes bv 

 Brehm (54). 



§ Not actually recorded from the lake itself, but from within its drainai2;e area. 



