300 ORTMANN — DISTRIBUTION OF DECAPODS [Aprils, 



the very incompletely known Erimetopus of Rathbun. The value 

 of a few other genera, created by various authors, is extremely 

 doubtful. 



Parathelphusa is represented by typical species in the northern 

 parts of India, in Burma, Siam, Anam, Malacca, Southern China 

 (Hongkong and Canton), and in the Sunda Islands: Sumatra, 

 Borneo, Java, extending to Timor and New Guinea. With the 

 same genus some other forms have been classified which are found 

 in certain parts of Africa (Congo basin and Nile river j ; but these 

 have been placed by the present writer in a subgenus (Acanthothel- 

 phusa) of Potamon, since they differ in their general shape very 

 strikingly from the Asiatic species of Parathelphusa. Unfortunately 

 these African species are very poorly known ; only of the Nile 

 species figures have been published (Milne-Edwards and Hilgen- 

 dorf), and according to these it is impossible to unite this species 

 and its supposed allies with Parathelphusa} 



As regards the genus Potamon, it is divided into several sub- 

 genera, which, however, are not very sharply defined. Aside from 

 the doubtful subgenus Acanthothelphusa just mentioned, there are 

 three of them which are generally recognized : Potamon (sens, 

 strict.), Potamonautes Macl., and Geothelphusa Stps. 2 



The centre of the subgenus Potamon is, no doubt, in India and 

 Farther India. Thence it extends eastward to the greater Sunda 

 Islands (Sumatra and Java) ; it is found in the Philippine Islands, 

 but does not advance any farther in this direction. Northward it 

 enters China, where it is known from the Yang-tse-Kiang (see 

 Doflein, 1902, p. 662). It does not seem to pass beyond the 

 Himalaya Mountains to the north, but extends considerably west- 

 ward (possibly in a single species), going through Persia to the 

 Transcaspian countries, crossing the Caucasus Mountains and 

 extending to the Crimea ; from Mesopotamia it extends to Syria and 

 Asia Minor, where it reaches the Mediterranean countries, and here 

 it is found in Northern Egypt, Turkey, Greece, Italy, Sicily, and 



1 Possibly Platythelphusa A. M.-E. (see Hilgendorf, 1898, p. 21) from Lake 

 Tanganyika also belongs here. 



2 1 disregard, for the present, the subgenus Perithelphusa de Man (1899, 

 p. 70), which contains apparently rather primitive forms of Geothelphusa, and, 

 on account of its exclusive occurrence in Borneo, may be left united with 

 Geothelphusa. As to Platythelphusa, see the last note. As to Hydrothelphusa 

 A. M.-E., see below. 



