BY CHARLES CHILTON, M.A. 1039 



In all my specimens the terminal pleopoda have been broken 

 off, hence they were ])robably of large size. In their absence it is 

 impossible to say whether this species is a Mo&ra or a Mdita. 



MCERA SUBCARINATA. 



Megam(ERA sub-carinata. Haswell. 



Cat. A list. Crust., p. 260 ; Proc. Linn. Soc, N. S. Wales, IV., 

 p. 335, PI. XXL, fig. 4. 



McERA PETRIEL G. M. Thompson. 



Trans. N. Z. Inst., XIV., p. 236. 



Among algae in Sydney Harbour I took at low water several 

 specimens which on examination proved to be without doubt the 

 same as Mcera petriei Thomson, a species fairly common in 

 Lyttelton Harbour, and after a careful comparison of the two 

 descriptions, I have no doubt that this species is the same as 

 Megaimera sub-carinata, Haswell. I am by no means sure of the 

 generic impoittmce of the differences separating Megammra from 

 Mosra, and therefore prefer to place the species under Mcara as 

 Mr. Thompson has done. 



The only point in which the two descriptions really differ is with 

 regard to the length of the superior antennje That of Mchra jyetriei 

 is " as long as the body " while that of Megamuira sub-carinata 

 is "nearly as long as the cephalon and pereion ;" the length of the 

 suj;)erior antenna however, varies in this s))ecies as in many others 

 of the Amphipoda. 



I have both male and female specimens from Sydney, the females 

 agreeing with the description given by myself in Transactions 

 N. Z. Institute, XV., p. 82. Curiously enough the males 

 agree with those described by Mr. Thomson and differ from my 

 Lyttelton specimens in having the " whole lower surface (ot the 

 propodos of the posterior gnathopoda) very densely fringed with 

 two rows of long simple hairs." These hairs which are of the 

 same size throughout their whole length and thus differ from the 

 ordinary setae found in this genus are quite absent in the Lyttelton 

 specimens. An interesting question thus arises, but must for the 

 present remain unanswered — what is the function of these hairs 

 and why should specimens from Sydney and Stewart Island have 

 them while those from Lyttelton have not ? 



