93 



NOTE ON THE OCCURRENCE IN TASMANIA OF 

 THE FRESHWATER CRAB, HYMENOSOMA 

 LACUSTRIS, CHILTON. 



By Chas. Chilton, M.A., D.Sc, C.M.Z.S., 



Professor of Biology, Canterbury College, New Zealand. 

 (Communicated by Professor T. Thomson Flynn.) 



(Received 8th July, 1919. Read Ilth August, 1919.) 



Professor T. Thomson Flynn, of the University of 

 Tasmania, of Hobart, has been good enough to send me 

 some specimens of a small crab obtained by him in NoiiJi- 

 West Tasmania, which he thought belonged to the species 

 Hyinenondina lacuxfrls, Chilton, though they appeared to 

 differ from the published descriptions in the shape of the 

 roatrum and in some other points. The few specimens he 

 collected were found nestling in the crevices of i-otting 

 wood in a very small creek in the middle of an open pad- 

 dock near Flowerdale. 



This species was originally described from .specimens 

 obtained in Lake Takapuna, near Auckland, New Zea- 

 land, and has since been recorded fx-om other localities in 

 Now Zealand, also from Norfolk Island, Lord llowo 

 Island, and from two localities in Victoria, Australia. Itis 

 occunence in Tasmania is additional evidence of its wide 

 distribution, and its antiquity. I have compared the Tas- 

 manian specimens with those from the other localities, 

 and consider that they should be placed in the same 

 species. The rostrum is more shaq)ly depressed than in 

 the Victorian specimens, more truncate at the end, and 

 its lateral margins are more raised, showing prominently 

 in dorsal view. In the Victorian specimens the rostrum 

 is more nearly horizontal, its margins are less prominent, 

 and the end is somewhat narrowly rounded. The Nor- 

 folk Island specimens have the rostrum, on the whole, 

 similar to that of the Victorian, but the end is more 

 broadly rovmded ; in the Lake Takapuna specimens the 

 roetiiim is much depressed, and the margins are sharply 

 raised, but the end narrows to a blunt point, instead of 

 being regularly rounded. 



Other differences between the specimens then known in 

 the lateral teeth on the carapace, the hairiness of the cara- 



