Crustacea.] SUBANTARCTIC ISLANDS OF NEW ZEALAND. 637 



Some of these species have been referred to Parorchestia, others to Talitrus, and 

 others again to Orchestia ; and in some cases the same species appears to be very 

 widely distributed : thus, Orchestia platensis Kroyer has been recorded from Kio 

 de la Plata, in South America ; the Atlantic coast of North America ; Bermudas ; 

 the Mediterranean ; the Lake of Tiberias, in Palestine ; from the Hawaiian Islands, 

 where it is found at a height of 3,000 ft. ; and Mr. Walker has even recorded it from 

 the Mahlosmadula Atoll, in the Indian Ocean, at a depth of 20 fathoms in the sea.* 

 Some of these identifications, however, appear to have been founded only on female 

 specimens, and, as is well known, it is in many cases almost impossible to distinguish 

 species of this group by the females alone. 



In this paper I describe four new species of Parorchestia, three of which are 

 distinguished by the characters of the adult male ; with two of these it is practically 

 impossible to distinguish the females from one another or from those of P. sylvicola, 

 the species so abundant on the main islands of New Zealand. It may be, of course, 

 that in this instance we are dealing with one widely spread species with polymorphic 

 males ; but, as the forms so far as is at present known are confined to separate 

 islands, I prefer to look upon them in the meantime as distinct species. f 



The fourth species, P. imfrovisa, of which only the female is known, is remark- 

 able for having the propod of the first gnathopod enlarged and completely subchelate 

 and similar to that of the second gnathopod of the males in other species, though 

 developed to a less degree. 



Parochestia maynei, sp. nov. 



Male. — Body moderately compressed, side plates not very deep, hfth as deep 

 as the fourth, pleon segments with the lower margins somewhat rounded, posterior 

 angle of the third quadrate. Eyes round, as far apart as their width. First antenna 

 reaching to the end of the fourth joint of peduncle of the second, its third joint much 

 longer than the first or second, which are subequal ; flagellum six- jointed, as long 

 as the third joint of peduncle. The second antenna slender, more than half as long 

 as the body ; fifth joint of peduncle one and a half times the length of the fourth, 

 bearing a few fine setae ; flagellum rather longer than peduncle, about thirty -jointed, 

 joints rather longer than broad, slightly expanded distally, each with four stiff setae 

 longer than the joint is wide. First gnathopod (fig. 7c) with basos slender; merus 

 with a slight pellucid enlargement at the distal end ; carpus considerably longer 

 than the propod, its posterior margin produced into a rounded pellucid lobe, the 



* " The Fauna and Geography of the Maldive and Laccadive Archipelago," vol. ii, Supplement 1, 

 Amphipoda, pp. 923, 924. 



f I have spoken of these forms in the usual way as if they are simply males and females distinguished 

 by constant differences. It is quite possible, however, that their relation is more complex, and that, 

 e.g., the distinctive characters of the males are attained only during the breeding season, and that at 

 other times the secondary sexual characters are poorly developed. In this case we would have some- 

 thing approximating to the " high and low dimorphism " so common in the Lamellicorn beetles and 

 to the case described by Geoffrey Smith in the crab Inachus mauritanicus ; he considers the condition 

 of the " middle-sized males " in this species as one of partial hermaphroditism, and draws attention 

 to the partial hermaphroditism described by C. L. Boulenger in Orchestia. In these, however, the small 

 ova appear to be developed only in young males in which the secondary sexual characters are not well 

 developed, the gnathopods being scarcely differentiated. (See Geoffrey Smith, " Cambridge Natural 

 History," Crustacea, pp. 102-4, and C. L. Boulenger, P.Z.S., 1908, pp. 42-47.) 



