MORPHOLOGICAL AND GEOGRAPHICAL GROUPS. 313 
crayfishes is not recorded; in the Japanese 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 Cambari. Unfortunately, nothing is known as to 
the branchie of the Amurland crayfishes. According 
to De Haan, those of the Japanese species resemble 
those of the western Astact: as those of the West 
American Aséaci certainly do. 
With respect to the Parastacide; 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. 65) and in the extreme modification of its branchial 
system, which I have described elsewhere, the Madagascar 
genus stands alone. 
The Paranephrops of New Zealand and the Fijis, with 
its wide and short epistoma, 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 
