734 ON A NEW ISOPODAN GENUS (FAMILY ONISCIDAE)- 



marine in its flora. Moreover Lake Colac, which is situated 

 only a few miles away, is fresh and in its waters lives the little 

 freshwater crab Hymenosoma lacustris found in fresh water 

 streams and lakes in Australia, Tasmania, New Zealand, Nor- 

 folk Island and Lord Howe Island,* thus apparently showing 

 that the places where it is found cannot have been submerged 

 below the sea for a period extending sufficiently far back in the 

 past to account for its present wide distribution. 



On the whole therefore I incline to the opinion that Halonis- 

 cus is the descendant of a form that was terrestrial in habits 

 and that, owing to the special circumstances arising from its 

 habitat, it has become re-adapted to aquatic life. 



I wi i\ to record my thanks to Professor W. A. Haswell and 

 Mr. J. dearie for the opportunity of examining and describing 

 this Isopod, and to Miss E. M. Herriott, M.A., Assistant at 

 the Canterbury College Biological Laboratory, for the care and 

 accuracy with which she has prepared the figures illustrating 

 the paper. 



•Chilton. Trans. N.Z. Inst., Vol. 47, p. 316, and Proc. Roy. Soc 

 Tasmania, 1919, p. 93. 



