REPORT ON THE CUMACEA. 45 



smooth, without denticles. First pair of legs scarcely longer than carapace, with the 

 three outer joints subequal ; second pair with antepenultimate joint longer than the two 

 outer taken together. Telson rather elongate-, with terminal part much longer than basal, 

 and densely spinous at both edges ; apical spines not larger than lateral. Uropoda with 

 scape very slender, branches subequal, about half as long as scape, inner distinctly 

 triarticulate. Length of female, 16 mm., of adult male, 21 mm. 



Remarks. — The present species was briefly described by the author in the year 1873, 

 from a single young female specimen obtained during the Swedish Spitzbergen Expedition 

 in 1868, from the very considerable depth of 2600 fathoms. During the Challenger 

 Expedition several specimens, both females and adult males, were procured, and I thus 

 have had an opportunity of making a closer examination of this form, to show the very 

 striking differences between the two sexes, as regards both the general appearance and 

 several of the anatomical details. 



Description of the Female. — The length of the adult specimens is about 16 mm., and 

 the present form thus belongs to the larger species of the order. The form of the body 

 (see PI. VI. figs. 1, 2) is rather stout, with the anterior division considerably dilated, 

 nearly ovoid in form, and sharply marked off from the slender tail. 



The carapace is very large and deep, about twice as long as the exposed part of the 

 trunk, and nearly as broad as high. The dorsal surface is strongly vaulted in its 

 posterior part, declining anteriorly to the base of the pseudorostral projection. The 

 latter is conical in form and of moderate length, about as long as the frontal lobe. The 

 inferior edges of the carapace are somewhat irregularly arched, without forming any 

 distinct antero-lateral corners ; they are finely serrate in the anterior part, and join the 

 posterior edge without being defined from it by any distinct angle. The surface of the 

 carapace appears everywhere evenly arched, without any folds or keels, but is beset with 

 numerous small equal-sized spinules, more densely crowded in the anterior part. 



The exposed part of the trunk consists of five well-defined segments, rapidly decreasing 

 in height posteriorly. The first segment is very narrow, almost band-like, and the three 

 succeeding segments only slightly increase in length, all these segments being firmly 

 connected with each other. The last segment is very small and rather movably connected 

 with the preceding, a space covered by thin skin being interposed dorsally between the two 

 segments. On all the segments the lateral parts form small rounded epimeral plates, 

 slightly projecting laterally. Those of the last segment are somewhat produced 

 posteriorly, without, however, forming acuminate projections as in the adult male. The 

 first three segments have the anterior margin very finely denticulate, and this is also the 

 case with the last segment, which also bears two small dorsal denticles. 



The tail is scarcely longer than the anterior division of the body, but very slender 

 and cylindrical, with the posterior margin of the segments strongly emarginate both 

 dorsally and ventrally, and forming on each side a slight projecting angle. The three 



