Crustacea.] 



SUBANTARCTIC ISLANDS OF NEW ZEALAND. 



633 



Fig. 4. — Urchestia serrulatu, Dana. 

 Side view of a large male. 



to be these two forms, it is perhaps best to keep them as separate species, though 

 they are certainly very closely related. There is nothing mentioned in either Dana's 

 or Spence Bate's descriptions about the corrugations. I am therefore following 

 Stebbing in referring the corrugated form to 0. 

 serrulata, Dana. 



The distinctive characters of this species are 

 to be seen only in fully adult males, the females 

 and the immature males being very difficult to 

 distinguish from those of other closely allied 

 species of the genus. In the fully developed males 

 the second antenna is about half the length of the 

 body, with the peduncle smooth and somewhat 

 angular in section, its last two joints very long ; 

 the flagellum contains about twenty joints, and 

 may be slightly longer than the peduncle, though 

 often somewhat shorter ; the whole appendage is smooth, being almost free from 

 setae. The second gnathopod of the male (fig. 56) has the propod very largely 

 developed, nearly as broad as long, the palm nearly transverse, and defined, by a 

 stout sharp tooth, on the inner side of which the finger impinges ; near the base of 

 the finger the palm is deeply hollowed out, and near the middle it is produced to 

 a subacute tooth, from which it extends almost straight to the defining-tooth ; 

 the finger is strongly curved, so that its inner margin is very concave ; a few short 

 setae are present on the basos and. on the palm, but the rest of the joint is almost 

 quite smooth. In the fifth peraeopod 

 (fig. 5c) the basos has the posterior flat 

 expansion somewhat narrow, its pos- 

 terior margin being straight or only 

 very slightly convex and only obscurely 

 serrate, and the lower angle is pro- 

 duced into an acute process reaching 

 beyond the extremity of the ischium; 

 the distal end of the merus is deeply 

 concave, the anterior angle being pro- 

 duced into a distinct tooth, curving 

 slightly inwards, the posterior angle 

 being much less produced ; the carpus 

 is slightly longer and considerably 

 broader than the propod, and both 

 bear a few short setae on the anterior 

 margin ; the finger is short and stout. 



In younger males the setae on the 

 various appendages are much more 

 prominent, the antennae are shorter in proportion to the length of the body, the 

 second gnathopod has the propod smaller and the palm much straighter and the 

 finger less curved ; in the fifth peraeopod the basos has the posterior expansion 

 slightly wider in proportion to the length of the joint, its posterior margin some- 

 what convex and more distinctly serrate, and the lower angle less produced, 



Sa 



Fig. 5. — Orchestia .serrulata. Dana. 



5a. First gnathopod of large male. 

 56. Second gnathopod of large male. 

 5c. Fifth peraeopod of large male. 



