302 ORTMANN — DISTRIBUTION OF DECAPODS [April 3, 



The main range of Potamonautes in Africa seems to be almost 

 continuous, but absolutely isolated from it is a secondary centre in 

 South Asia. Here this subgenus is represented in India, and 

 thence it extends to Farther India, and reappears on some of the 

 islands : Pulo Condore on the coast of Cochin China, in the Philip- 

 pine Islands, Celebes and New Guinea. These latter localities are 

 distinctly discontinuous. 



The third subgenus, Geothelphusa, undoubtedly has its centre in 

 the extreme East, and it is most characteristic for the Malaysian 

 Islands. On the Asiatic continent it seems to be absent ; but it is 

 found abundantly in Sumatra, Java, Borneo, and extends eastward 

 over Aru Island and New Guinea to North Australia, where it is 

 found on the Cape York Peninsula, and in Queensland as far as 

 Port Mackay. 1 Northward this subgenus ranges over the Philippine 

 and Loo-Choo Islands to Japan, where it reaches its northernmost 

 station in the neighborhood of Tokyo. 



On the continent of Asia typical species of this subgenus have 

 not been found ; indeed a few small species from India have been 

 described which might be united with this subgenus, but this is by 

 no means sure. 



But this identical subgenus, Geothelphusa, is apparently found in 

 another locality isolated from the rest of the range : this is 

 P. b er ardi (Aud.) from Egypt (Nile river). This species, however, 

 is also morphologically isolated from the rest ; and further, this 

 subgenus is recorded by Rathbun from Liberia {P. macropus'Rxhb., 

 1898), and some species from East and Central Africa, related to 

 P. obesum, mentioned above, resemble, in the reduction of the 

 postfrontal crest, the subgenus Geothelphusa, 2 while on the other 

 hand they are undoubtedly related to the subgenus Potamofiautes. 

 It is quite possible also that P. berardi from Egypt (Kairo south- 

 ward to Mount Elgon) belongs to this East African group. In my 

 opinion, all these species do not properly belong to Geothelphusa, 

 and we have to deal here again with a case of convergency: the 



1 According to de Man, an Australian species [P. transversum (Mrts.)) is also 

 found in the Fiji Islands ; but this lacks confirmation. 



2 These are P. obesum (A. M.-E ), Zanzibar; P. e?nini Hlgdf., P. new- 

 manni Hlgdf., P. pilosum Hlgdf. (Hilgendorf, 1898), all three from East 

 Africa and the region of the Great Lakes. Possibly P. socotrense Hilgendorf 

 (1883, Zeitschr. d. Naturw., Ser. 4, Vol. 2) — P. granosum Koelbel [SB. 

 Akad. Wien, Vol. 90, 1885) belongs here. 



