STUDIES IN AUSTRALIAN CRUSTACEA. 



No. 4. * 

 By Allan R. McCulloch, Z(3ologi«t, Australiau Museum. 



(Plates xlii-xliii.) 



AUSTRALIAN FRESH-WATER CRABS. ^ 



(Plate xlii.) 



The identification of the several species of Fresh-water 

 Crabs occurring in Australia is a matter of considerable 

 difficulty. This is partly due to the fact that references to 

 them in literature are both scanty and incomplete, but a 

 greater difficulty is presented by the remarkable degree of 

 variation which they exhibit in characters which are recog- 

 nised as constant in marine species. 



The extraordinary uniformity of climatic and other condi- 

 tions prevailing over a large portion of Australia, combined 

 with a close intermingling of the river systems, has enabled 

 many of our fresh-water animals to distribute themselves over 

 an exceedingly wide area. Some fishesi for example, are 

 known to range from the western waters of New South Wales 

 to Central, North, and Western Austi'alia; though they 

 pi-esent remarkable variations in both form and colour-mark- 

 ing, they cannot be subdivided even into geographical sub- 

 species, as is readily proved by a lai'ge series of specimens 

 collected from various widely separated localities. Similarly, 

 the Yabbie, ParachieraiJtt hicariiiatus^, ranges from Victoria to 

 Queensland, Central and North Australia, and perhaps reaches 

 the Western State, but though it exhibits marked variation in 

 all parts of its range, it nevertheless appears indivisible into 

 subspecies. Though more restricted in their distribution, the 

 Fresh-water Crabs of Australia appear to be equally variable, 

 and in the absence of ample material from numerous localities, 

 it seems to be impossible to determine the true relationship of 

 the different forms to one another. 



* For No. 3 see Vol. ix., p. 321. 



1 Ogilby and McCulloch— Mem. Qld. Mus., v., 1916, pp. 101, 106, 110. 



aSmith— Proe. Zool. Soc, 1912, pp. 147, 163. 



