i8o THE LIFE OF CRUSTACEA 



that live in fresh water. Some of these, like the 

 species of Sesarma (see Plate XXIII.) and some other 

 genera of the family Grapsidae, are common through- 

 out the tropics, passing up the rivers from the 

 brackish water of estuaries, and being often found 

 long distances inland in quite fresh water. The true 

 River Crabs, however, belong to the family Potamo- 

 nidae, and are very common throughout the warmer 

 regions of the globe. One species, Potamon edule 

 (Plate XXIII.), formerly called Telphusa fluviatilis, is 

 found in the South of Europe (Italy, Greece, etc.). 

 Very numerous species, as yet only imperfectly 

 known, occur throughout the whole of Africa, in 

 Southern Asia, and in the Malay Islands, extending 

 to Australia in the south and Japan on the north. 

 In the New World the River Crabs are found in 

 South America, and extend north to Mexico and the 

 West Indian Islands. Many of the River Crabs are 

 amphibious in habits, and may be found burrowing 

 in marshy ground or in damp forests. The young 

 are hatched from the egg with all the appendages 

 developed, and they remain clinging to the abdomen 

 of the mother until after the first moult, when they 

 are perfectly-formed little crabs (see Fig. 31, p. 78). 



The groups which have been mentioned are all 

 characteristic inhabitants of the fresh waters over 

 considerable areas of the surface of the globe. There 

 are, however, in addition to these, certain Crustacea 

 which occur in isolated localities, and have no close 



