REPORT ON THE CUMACEA. 43 



segments taken together, with the scape cylindrical and armed with a row of about 

 twelve small spines along the inner edge. Both l^ranches are biarticvilate, as in the 

 genus Leucon, and on the whole agree fairly well in structure with those in that genus. 

 The inner branch is much the longer, slightly tapering towards the tip and armed with 

 a regular row of denticles along the inner edge. Its terminal joint is very short and 

 has at the tip a strong spine and an elongate seta, besides four small denticles aloug 

 the inner edge. The outer branch is scarcely longer than the first joint of the inner, 

 and has the basal joint rather short and obliquely truncate at the end, whereas the 

 terminal joint is elongate and somewhat compressed, with a row of about ten strong 

 ciliated setse along the inner edge and at the tip. 



Habitat. — The above described specimen was taken with the trawl from a very 

 considerable depth in the North Atlantic, off the coast of the United States. 



Station 45, May 3, 1873 ; lat. 38° 34' N., long. 72° 10' W.; depth, 1240 fathoms; 

 bottom, blue mud; bottom temperature, 37°'2. 



Family V. DlASTYLlD^. 



The Cumacea referred to this family are easily known by the tumid and ovate form 

 of the anterior division of the body, which is sharply marked off from the slender and 

 very mobile tail ; also by the large, superiorly strongly arched carapace terminating in 

 front in a more or less prominent rostriform projection, and finally by the distinctly 

 defined, lageniform telson, and the great length of the scape of the uropoda. The 

 family at present comprises only two genera, ^^iz., Diastylis, Say, and Leptostylis, G. 0. 

 Sars. Of these only the first is represented in the Challenger collection. 



Genus Diastylis, Say, 1817. 



DiasfyNs, Say, Journ. Acad. Nat. Sci. Philadelphia, 1817. 



Condijlura, Latreille, Le Eegne Animal, t. iv. p. 153, 1829 (not Illiger). 



Alauna, Goodsir, Edin. New Phil. Journ., vol. xxxiv. p. 130, 1843. 



Cuma, Kroyer, Nat. Hist. Tidsskr., Bd. iii. p. 530, 1841 (not Milne-Edwards). 



Generic Characters. — Form and armature of body generally rather dissimilar in the 

 two sexes, adult male always much more slender than female. Carapace large and 

 tumid, mostly spinous, antei'o-lateral corners obsolete, pseudorostral projection triangu- 

 larly pointed. Eye present or wanting. Antennulse slender, j^eduncle only slightly 

 thickened in male. Antenna in female four to five-articiilate, in male very fully 

 developed, attaining the length of the body, distal part of peduncle composed of 

 a single large segment with numerous fascicles of small sensory appendages along the 

 outer edge, flagellum very slender, with elongate articulations. First pair of legs more 



