634 SUBANTARCTIC ISLANDS OF NEW ZEALAND, [Crustacea. 



forming often only a right angle ; the merus is less broadened, and its distal 

 extremity more of the usual shape. 



The females agree with the younger males in all these points, and apparently 

 differ only in the gnathopods : in the first gnathopod the propod is about the same 

 width throughout, with the palm very small and the finger projecting beyond it ; the 

 second gnathopod presents no distinct features. 



Orchestia aucklandiae, Spence Bate. 



Orchestia aucklandiae, Spence Bate, Cat. Amphip. Brit. Mus., p. 17, pi. ia, 

 fig. 3, 1862 ; G. M. Thomson, Trans. N.Z. Inst., xxxi, p. 201, 1898 ; 

 A. 0. Walker, Ann. & Mag. Nat. Hist., ser. 8, ii, p. 36, 1908. Orchestia 

 serrulata (part), Stebbing, " Das Tierreich Amphipoda," p. 535, 1906. 



Several specimens, both male and female, from Enderby Island are certainly 

 the same as those from the same locality referred to this species by Mr. Walker, and 

 I think he is right in referring them to Spence Bate's species. They agree well with 

 the description given by Mr. Walker, and, although they come very close to the 

 preceding species, they differ from it in the absence of the transverse ridges or corru- 

 gations on the segments of the peraeon even in large specimens, for some of the 

 specimens are larger than specimens of the preceding species in which these trans- 

 verse ridges are nevertheless present. The females have the distal end of the first 

 gnathopod as wide or slightly wider than the base, and thus agree with the descrip- 

 tion given by Mr. Walker, and differ from that given by Mr. Stebbing for 0. serrulata. 



I am therefore following Walker in considering these specimens to belong to a 

 species distinct from 0. serrulata, though I quite realise that good reasons may be 

 urged for combining the two. 



Mr. Walker states that his specimens might well be referred to 0. gammarellus, 

 Pallas," but for the absence of the expansion of the fourth and fifth joints of peraeo- 

 pod 5," and he adds that it is by no means certain that his specimens were sexually 

 adult. Some of my specimens are adult females bearing eggs, and the largest males 

 measure about 24 mm. in length, and are most probably also adult ; but in none 

 of them is there any sign of the expansions referred to. 



The second gnathopods of the male vary considerably in the appearance of the 

 margin of the palm, according to age ; but even in the largest specimens the excava- 

 tion near the base of the finger is not great, while in younger specimens the palm 

 is almost straight and the finger fits closely along it. Spence Bate describes the finger 

 as being " excavated near the base," but this appearance is rather due to a curva- 

 ture of the finger at that point, so that the inner margin becomes concave ; in younger 

 specimens the finger is straighter. The fifth peraeopod clossly resembles that of the 

 preceding species in having the posterior expansion of the basos angular and pro- 

 duced downwards, the amount of this downward production varying greatly with 

 the age and sex of the specimen, in young males and in females the lower inferior 

 angle being a right angle ; the posterior margin is straight or slightly convex and 

 more or less serrulate, and the whole of the posterior expansion is clearly marked 

 off on the outer side from the thicker anterior portion of the basos. The end of 

 the merus is excavated, and the anterior and posterior margins produced downwards 

 into two short spines, the anterior one being the longer, these spines being better 



