THE NAUTILUS. 



VOL. XII. AUGUST, 1898. No. 4. 



THE MOLLUSKS OF THE GKEAT AFRICAN LAKES 



Mr. J. E. S. Moore has recently studied the Mollusk fauna of the 

 African Lakes Nyassa and Tanganyika, and has recorded a portion 

 of his results, which prove to be of very great interest. 1 



It is pointed out that the molluscan genera constituting the lake 

 faunas of Africa fall into two categories; those genera more or less 

 widely distributed in Africa such as Unio, Spat ha, Iridina, Corbie- 

 nla, Limn (fa, Isidora, Plaiiorbis, Ancylus, Ampnllaria, Vivipara, By- 

 thinia, Melania and their immediate allies, these constituting a per- 

 fectly normal group, all or most members of which occur in most of 

 the lakes yet explored. The second group comprises TypJwbla, 

 Nassopsis, I/imnotrochus, Syrnolopsis, Tanganyitia, Bathanalia, Para- 

 melania, Bythoceras and some other forms, and is confined to the 

 single lake Tanganyika. This series of genera is called by Mr. 

 Moore the " Halolimnic group." With few exceptions, they are 

 deep water forms, mainly ranging from 200 to 1000 ft. which was 

 the greatest depth reached, while the species of the " normal " group 

 of genera live mainly within the 100 ft. line. After a thorough 

 discussion of the geological and biological aspects of the case, Mr. 

 Moore concludes that the Haloiimnic mollusks in Tanganyika owe 

 their origin to an ancient connection with the sea. 



1 Proc. Eoy. Soc., LXII, no. 387, March 29, 1898. Quarterly Journ. Mic. 

 Sci., XLI, pt. 1, p. 159, March, 1898. 



