521 



normal. Gnathopoda subcheliform, and ratber unequal, the posterior ones 

 being much the larger, and very strongly developed in the male. Posterior 

 pairs of pereiopoda unusually robust, with the joints more or less expanded, 

 and the basal one very large and laminar. Last pair of uropoda not very much 

 elongated, and somewhat robust in structure, with the rami comparatively 

 broad. Telson laminar, and divided by a deep and narrow cleft into two 

 halves, each spinous at the tip. 



RemarJcs. — The present genus, established by Costa, is chiefly distin- 

 guished by the short and robust body, the powerful development of the 

 posterior gnathopoda, the unusually strongly built posterior j)airs of pereiopda, 

 and the structure of the last pair of uropoda and that of the telson. 

 Besides the typical species described below, Mr. Stebbing has recorded 2 

 species from the Challenger Expedition, and Boeck says that he has 

 examined species of this genus, both from the west coast of America, and 

 from South Africa. 



21. Elasmopus rapax, Costa. 



(PI. 183). 



Elasmopus rajiax, Costa, Crusl. Ampliip. del Regno di Napoli, p. 212, PI. IV, fig. 5. 



Syn : Megamsera brevicaudata, Sp. Bate. 

 > Msera brevicaudata, Heller. 

 » Elasmopus latipes, Boeck. 



Body short and stout, with the back evenly rounded and smooth 

 tliroughout. Cephalon fully as long as the first 2 segments of mesosome 

 combined, lateral corners broadly rounded, and having below them a projecting 

 lobe obtuse at the tip. Anterior pairs of coxal plates fully as deep as the 

 corresponding segments, 1st pair angularly produced in front, 4th pair with 

 the posterior expansion obliquely truncated. Last pair of epimeral plates of 

 metasome scarcely produced at the lateral corners, posterior edge irregularly 

 indented in its lower part. Eyes rather large and rounded oval in form, 

 pigment very dark. Superior antennae about half the length of the body, 

 1st joint of the peduncle nearly as long as the 2nd, and considerably thicker, 

 3rd joint exceeding half the length of the 2nd, flagellum not quite as long as 

 the peduncle, and composed of numerous short articulations, accessory 

 appendage not attaining the length of the last peduncular joint, and 

 biarticiilate. Liferior antennse considerably shorter than the superior, the 

 last 2 joints of the peduncle nearly equal-sized, flagellum not attaining the 

 length of those joints combined. Anterior gnathopoda with the propodos 

 longer than the carpus and somewhat expanded, oval quadrangular in form, 



