178 



THE LIFE OF CRUSTACEA 



corded from New Guinea, but no Crayfishes are found 

 in any part of the Malay Archipelago, in Southern 

 Asia, or on the continent of Africa, although, 

 curiously enough, a single species of a peculiar 

 genus (Astacoides) is found in Madagascar. In South 

 America species of Parastacus are found in Southern 

 Brazil, Argentina, and Chili. It is evident that 

 these various genera of Parastacidse, which are now 

 so widely isolated from each other, must have reached 

 their present habitats when the relative distribution 

 of land and sea in the Southern Hemisphere was 

 very different from what it is now. What exactly 

 the nature of the land connection between the various 

 islands and continents was, whether by way of an 

 Antarctic continent or otherwise, is a question that 

 can only be suggested here. To attempt to answer 

 it would involve the consideration of the distribution 

 of many other groups of animals besides Crayfishes. 

 Before leaving the Crayfishes, it may be mentioned 

 that certain species have become adapted to almost 

 terrestrial habits. A number of species of Cambarus 

 in North America are often found at considerable 

 distances from open water, burrowing in damp earth, 

 their burrows reaching down to the ground-water. 

 In many cases they throw up chimney-like piles of 

 mud at the mouths of their burrows, and in places 

 their chimneys are so numerous as to " hamper 

 farming operations by interfering with the harvesting 

 machines, clogging and ruining them." The species 



