294 THE TANGANYIKA PROBLEM. 



about 50 species, of which only two are said to be marine. It is closely allied to 

 Leander, in which, conversely, the marine species greatly predominate, while both 

 genera have numerous allies among the littoral fauna. 



Limnocaridina belongs to the Atyidce, a circumtropical family of freshwater 

 forms whose probably somewhat distant allies are supposed by Ortmann to be found 

 in the deep-sea Acanthephyridie. It is a near ally of Caridina, an extensive genus, 

 of which one species is known from the West Indies, while the rest occupy 

 countries bordering on the Indian Ocean from S. Africa to Australia ; one species 

 occurs in the Nile and the rivers of Algeria. One species, C. wyckii, has a range 

 extending from East Africa to Queensland and Celebes. It is noteworthy from the 

 point of view of the present case that Caridina is not known to occur in West 

 Africa. Our form from Tanganyika is in the meantime an isolated species, and 

 the characters that it presents are not those of a primitive type, but rather of a 

 somewhat specialized form. 



