60 Proceedings of the Royal Society of Victoria. 



Hymenosoma lacustris. Chilton. Trans. N.Z. Inst., vol. 

 XV., p. 69, 1883. 



We have found this crab to be plentiful in the fresh waters of 

 Lake Colac, Victoria, and a single specimen collected by Mr. T. 

 S. Hall some years ago in the Moorabool River is undoubtedly 

 a young female of this species. The species was described by 

 Dr. Chilton in 1882 from specimens taken in Lake Pupuke — a 

 fresh-water lake near Auckland, N.Z. The author has kindly 

 furnished us with examples from the type locality and also with a 

 small series from Norfolk Island. As to these we observe that 

 those from the different localities differ slightly in the following 

 characteristics : — ■ 



From Netv Zeala?id. — In addition to the points set out in the 

 original description the following may be noted : 



The carapace has two obsolescent teeth on the anterior lateral 

 margins. 



The chelipedes of the male have the hand with the lower 

 posterior mai-gin faintly tuberculate, the wrist with only a very 

 small tubercle on its lower margin, and the arm with a small 

 tubercle on its distal outer margin. 



The specimens we have received from New Zealand are smaller 

 than those from Lake Colac, and about the same size as those 

 from Norfolk Island. 



From Lake Colac, Victoria. — The carapace has one obsolescent 

 tooth on the anterior lateral margins. 



The chelipedes of the male have the hand with the lower 

 posterior margin armed with 5-7 small rounded teeth and a 

 rounded tubercle in the median line near its articulation with the 

 wrist, the wrist with a prominent bifid tubercle on its lower 

 margin (in some cases cut into two distinct teeth) and the arm 

 without a tubercle on the distal outer margin. The specimens 

 are as a rule more hairy than those from New Zealand. 



The pleon of the male has a prominent tubercle on the outer 

 margin of the first somite, and less prominent ones on the second 

 and third. 



The outer maxillipedes are more cordate than in the New 

 Zealand form. 



From Norfolk Island. — The carapace is more nearly circular, 

 and is without marginal teeth. It is also generally more hairy 

 than either of the above. 



