42 



ON THE DISTRIBUTION AND HABITS OF THE 

 LARGE FRESH-WATER CRAYFISH (ASTACUS 

 SP.) OF THE NORTHERN RIVERS OF TASMANIA. 



By C. Gould, F.G.S. 



I trust that the members of this Society may bo interested 

 in a few remarks, which I have to make upon the distribution 

 and habits of the large fresh-water Crayfish which is so 

 common upon the north side of the island. 



I am not aware that this has been specifically described by 

 naturalists, although its unusually large size, abundance in 

 certain localities, estimation as a delicacy for the table, added 

 to its facility of capture and observation should long since 

 have acquired for it that attention at their hands. 



Leaving its determination, however, to those within whose 

 province it belongs, it is my purpose, as a field naturalist alone, 

 to offer the result of a few observations, and collate them with 

 other facts connected with the natural history of the island. 



And in the first place must be noted the remarkable repre- 

 sentative resemblance in most points, excepting size, of this 

 to members of the Genus Astacus of the Northern Hemis- 

 phere. 



Here we have yet one more of the many numerous examples 

 of a certain similarity in point of type, if not of close specific 

 resemblance, obtaining under equivalent conditions between 

 the forms of life at one extremity of the globe, and those 

 existing at the other, while strongly distinctive, but often 

 gradational peculiarities attend the forms controlled by the 

 opposing conditions of the intermediate tropical regions. 

 Hence the difficulty of referring the existence of such repre- 

 sentative or affinitive types to independent acts of creation — 

 and the apparently more sustainable solution by the theory of 

 biological metamorphosis. 



To instance 1st. The Rats and Mice among mammals ; 2nd. 

 Plovers, Eagles, Snipes, Ducks, Owls, and Thrushes amongst 

 birds ; 3rd. The Locusts and Painted lady and Admiral Butter- 

 flies amongst insects ; 4. The Ferns and Mosses among 

 plants, will be sufficient for my present purpose. 



I may next remark upon the limited nature of its distribu- 

 tion, as worthy of more than passing notice ; occurring more 

 or less abundantly in all the rivers upon the northern side of 

 the island, and being entirely absent from those upon the 

 south, it follows closely in its distribution that of the Black- 

 fish, with which it is always associated in the rivers falling 

 into Bass' Strait, with the one exception of the Esk, from 



