1906.] CRUSTACEA OF THE THIRD TANGANYIKA EXPEDITION. 203 



merus ; dactylus, includiiig terminal spine, about one-fifth of 

 propodus, with two spines on lower edge. Fifth perasopods 

 (Plate XI Y. fig. 71) with propodus longer than merus ; dactylus, 

 including terminal spine, one-fifth of propodus, with about 26 

 spines on lower edge. 



Total length, female (not ovigerous) 15 mm. 



Remarks. — This species is very similar to the preceding, but 

 appears to be sufficiently distinguished by the longer rostrum, the 

 longer sjoines on first segment of antennular peduncle, and the 

 smaller number of spines on dactylus of last perpeopods. 



Occurrence. — Mbete, 1.x. 04. " Taken on rocks, shallow water." 

 Two specimens. 



Kala, 19.xi.04. "Taken on rocks, shallow water." Two 

 specimens. 



iii. General Remarks. 



So far as the Macrurous Crustacea are concerned, the chief 

 result of Dr. Cunnington's Expedition has been to render still 

 more striking the great richness and peculiar character of the 

 fauna of Tanganyika as compared with that of the other lakes of 

 Central Africa. While Nyasa and Victoria Nyanza have yielded 

 only a single species which, with its varieties, has an enormously 

 wide geographical range from the Nile (and perhaps Algiers) to 

 Natal on the south, and to Queensland and New Caledonia on 

 the east, every one of the twelve species found in Tanganyika is, 

 so far as we yet know, peculiar to that lake. Of these, Palcmion 

 moorei belongs to a genus having a very wide distribution in the 

 fresh-waters of tropical regions ; but while a number of species 

 are known from East and West Africa, P. moorei is the only one 

 yet found in the region of the great lakes. Apai-t from its very 

 small size, the species does not present any very unusual or striking 

 characters, and it is therefore impossible to attach any great 

 importance, from the point of view of zoogeography, to its 

 supposed affinities with other species. It maybe noted, however, 

 that all the species with which it is found possible to compare it 

 closely are inhabitants of the East African and Oriental regions, 

 and that the species from the Nile, while undoubtedly distinct, 

 does not difier in such a way as to exclude the possibility of 

 phylogenetic connection. 



With the remaining eleven species, belonging to the Atyidas, 

 the case is very different. They represent three genera which, so 

 far as is yet known, are peculiar to Tanganyika, and which difier 

 from all the other genera of the family in having a smaller number 

 of branchiae. W^hether this single common character indicates a 

 phyletic connection between the three genera is doubtful. The 

 resemblances between Limnocaridina and Caridina, and between 

 Atyella and Atya or Ortmannia, would suggest that the reduction 

 of the gills had taken place independently in the two cases. At 

 the same time, Bouvier's very interesting discovery (C. R. Acad. 

 Sci. cxxxviii. p. 446, 1904, and Bull. Sci. France et Belgique, xxxix. 



