316 Transactions. 



Art. XXXIII. — A Fresh-water Crab, and its Distribution in Australia and 



New Zealand. 



By Charles Chilton, M.A.. D.Sc, M.B., CM., LL.D., F.L.S., Professor 



of Biology, Canterbury College, New Zealand. 



[Read before the Philosophical Institute of Canterbury, 2nd November, 1914.} 



In a small collection of Crustacea made towards the end of 1913 by Mr. 

 W. R. B. Oliver on Lord Howe and Norfolk Islands there is one specimen 

 of a small fresh-water crab, Hyiueiiosouia lacustris (Chilton), which was 

 obtained under a stone in a fresh -water stream on the top of Mount Gower, 

 about 3,000 ft. above sea-level, in Lord Howe Island. 



This crab is already known from some northern parts of New Zealand, 

 from Norfolk Island, and from localities in Victoria, and its occurrence 

 in Lord Howe Island is therefore of considerable importance, and affords 

 another link in the chain of evidence that will finally lead to the explanation 

 of its geographical distribution. A brief account of the history of tins 

 crab seems, therefore, desirable. 



It was described by myself in 1882 under the name Elamena (?) lacustris, 

 from Lake Takapuna (also called Pupuke), North Shore, Auckland. The 

 waters in Lake Takapuna are fresh ; but as the lake is only a very 

 short distance from the seashore, and there was no similar crab then 

 known from other fresh waters in New Zealand, I did not for some time 

 attach particular importance to its fresh-water habitat, but considered it 

 as being possibly a " relict '" form that had only recently adapted itself 

 to life in fresh water. A fuller knowledge of Lake Takapuna would, in 

 itself, have shown that this view was erroneous, as will be seen from the 

 account I give below ; but at that time little was known of the fauna of 

 the lake. 



In the next year (1883), having obtained further specimens, I re- 

 described the species and placed it under the genus Hymenosoma as defined 

 by Haswell in his catalogue of the Australian Crustacea published in 1882. 



Nothing more was added to our knowledge of this form till the year 

 1901, when. I received, through the kindness of Messrs. W. and R. M. Laing, 

 specimens from fresh-water streams in Norfolk Island which appeared to 

 me to be practically identical with the New Zealand species. About the 

 same time Mr. S. W. Fulton, of Melbourne, obtained specimens from Norfolk 

 Island, and also from Lake Colac, Victoria, and these, together with a 

 single specimen collected some years previously by Dr. T. S. Hall in the 

 Moorabool River, Victoria, also appeared to belong to the same species. 



I sent New Zealand specimens to Mr. Fulton for comparison with those 

 from the other localities, and, although he detected some slight local 

 variations, he found that they were all so much alike that in the account 

 published by himself and the late F. E. Grant in 1902,* he referred them 

 all to Hymenosoma lacustris (Chilton). 



About a year later Messrs. Lucas and Hodgkin. in their investigation 

 of some of the fresh-water lakes of New Zealand, obtained one male and 

 one female specimen from Lake Waikare, Auckland. These were after- 

 wards submitted to me for examination, and in my report published in 

 1906f were assigned to the same species, which was therefore evident!}" more 

 widely distributed in the northern part of New Zealand than I bad originally 



* Proc. Roy. Soc. Victoria, vol. 15 (n.s.), p. 59. 

 fP.Z.S., 1906, p. 702. 



