MORPHOLOGICAL AND GEOGRAPHICAL GROUPS. 313 



crayfishes is not recorded ; in the Jaj^anese crayfish, 

 judging by the figure given by De Haan, it is about the 

 same as in the western Astaci, On the other hand, in 

 the West American crayfishes it is distinctly smaller ; so 

 that, in this respect, they perhaps more nearly approach 

 the Canihari. Unfortunately, nothing is known as to 

 the branchiae of the Amurland crayfishes. According 

 to De Haan, those of the Japanese species resemble 

 those of the western Astaci : as those of the West 

 American Astaci certainly do. 



With respect to the Parastaciclce ; in the remarkable 

 length and flatness of the epistoma, the crayfishes of 

 Australia, Madagascar, and South America, resemble 

 one another. But in its peculiar truncated rostrum (see 

 fig. %d) and in the extreme modification of its branchial 

 system, which I have described elsewhere, the Madagascar 

 genus stands alone. 



The Paranepliro'ps of New Zealand and the Fijis, with 

 its wide and short e]3istoma, long rostrum, and large 

 antennary squames, is much more unlike the Australian 

 forms than might be expected from its geographical 

 position. On the other hand, considering their wide 

 separation by sea, the amount of resemblance be- 

 tween the New Zealand and the Fiji species is very 

 remarkable. 



If the distribution of the crayfishes is compared 

 with that of terrestrial animals in general, the points of 



