Chilton. — A Fresh-water Grab and it* Distribution. 



31 U 



the whole of New Zealand, and also occurs in fresh waters at the Chatham 

 Islands. It is not known from any part of Australia, but, curiously enough, 

 appears to occur again in Asfsam, specimens from this locality being in the 

 collections of the Indian Museum, and, according to Mr. S. Kemp,* prov- 

 ing to be indistinguishable from those obtained in New Zealand. On the 

 other hand, the fresh-water prawn known in Australia as X. compressa 

 (De Haan) extends as far as Norfolk Island, and though it is placed by 

 Bouvier in the same genus as X. curvirostris it differs markedly from that 

 species in the character of the rostrum. X. compressa is a species of wide 

 distribution, and extends from Australia right up to Japan. 



The former northern extension of New Zealand which seems necessary 

 to account for the distribution of the crab Hymenosoma lacustris seems 

 also indicated by the range of the large land-shell Placostylus,^ a genus 

 which is represented by two species in the north of New Zealand, and by 

 others in Lord Howe Island, New Caledonia, New Guinea, Fiji Islands, 

 New Hebrides, and Solomon Islands, and by the fact that the predominant 

 earth-worms in the North Island belong to the subfamily Megascolecinae, 

 which is characteristic of Australia and Tasmania, and is also represented 

 in Norfolk Island. J 



I append the following brief description : — 



Hymenosoma lacustris (Chilton). 



Elamena (?) lacustris Chilton, Trans. N.Z. Inst., vol. 14, p. 172. 



Hymenosoma lacustris Chilton, I.e., vol. 44, p. 128 (with synonymy). 



The chief points in the description of this crab may be given as follows : — ■ 



Carapace nearly circular, rather broader than long ; flat, naked, or with 



a few scattered hairs. Rostrum broad, strongly depressed, its upper surface 



Fig. 1. — Eymmosoma lacustris (Chilton), s ■ Drawn from Norfolk Island specimen. 



concave from side to side, extremity in form of an obtuse angle. Antero- 

 lateral margins of the carapace with 2 obscure teeth. Cheliped of male 

 small, propod only slightly broader than the carpus, hairy. Ambulatory 



*Kemp, S., "Notes on Decapoda in the Indian Museum, No. 4," Records Indian 

 Museum, vol. 7, p. 113. 



fSuter, H., "Manual of the New Zealand Moliusca," p. 763. 



t Benham, W. B., Trans. N.Z. Inst., vol. 37, p. 282, and vol. 35, p. 273. 



