256 Transactions. — Zoology. 



Length of largest specimen '56 inch. 



Hah. Lyttelton Harbour ; Worser Bay, Wellington (T. W. Kirk) ; 

 Port Jackson (W. A. Haswell). 



The differences between this species and Podocerus cylindricus, Say, have 

 already been mentioned in the general comparison of specimens from the 

 different localities ; but for the sake of greater clearness I will recapitulate 

 them. 



Flagellum of lower antenna is as long, or very nearly as long, as the last 

 joint of peduncle, the stout spines found on the end of it are not de- 

 veloped into hooks. The inner margin of dactylos of first gnathopod is only* 

 roughened in the female, and in the male the serrations, though sometimes 

 as great as in P. cylindricus, vary. The second gnathopod is larger than in 

 P. cylindricus, and is much larger in the male than in the female. In P. 

 cylindricus the female differs from the male only in " the slightly smaller 

 size of the propodos of second pair gnathopoda ; " the second gnathopod of 

 female also differs considerably in shape from that of the male. There is a 

 blunt tooth at the distal end of the concave margin of propodos (of male) ; 

 not found in P. cylindricus. The concave margin of the dactylos is smooth 

 in the male, in female roughened on proximal part only. 



These differences, though somewhat numerous, are none of them of very 

 great importance ; and, if P. cylindricus varies as much as P. longimanus, I 

 dare say it would be difficult to find constant differences of any importance 

 between the two species. In considering the question it must be remembered 

 that there are other similar cases : Paranthura costana, Philouyna rosea, 

 Lysianassa magellanica, Pinnotheres pisum, etc.: this, however, is not the 

 place to discuss the general question of the occurrence of the same species 

 in both the northern and the southern seas. 



Note. — My reasons for considering the two animals described above as 

 male and female of the same species are these : — (1) They resemble one 

 another so closely in everything but the gnathopoda that they must be 

 considered as belonging to the same species ; (2) the form with the small 

 gnathopoda is certainly a female, for I have frequently seen specimens 

 carrying eggs ; (3) the form with the large gnathopoda I have never seen 

 bearing eggs. 



The large gnathopoda of the male are only possessed by fully-grown 

 specimens. In very young animals they are more like those of the female, 

 having the palm extending only about half way along the inferior edge of 

 the propodos and defined by two or three stout seta?. In slightly older 

 specimens the palm is longer, until it extends along the whole length of the 

 margin of the propodos, and finally the setae are cast off and the gnathopod 

 assumes the form already described. 



