T. XIIl] CRUSTACEA CASPIA. 483 



evenly vaulted above, without any keels or projections, epiraera rather broad 

 and laminar. Metasome considerably longer than the anterior division of the 

 body. Eye well developed, with all 3 corneae distinct. Antennas and oral 

 parts of the usual structure. Legs comparatively slender; 2nd pair in male 

 modified in the same manner as in P. pectinata. Uropoda slender, with the 

 scape densely setiferous inside, and the rami equal-sized, both fringed inside 

 with slender spines. Telson very small, semi-elliptical. Length of adult female 

 about 5 mm, that of male nearly the same. 



Remarks. — The present species is at once distinguished from any of 

 the preceding ones by its extremely slender and elongated body, strongly 

 resembling in that respect some species of the genus Iphinoë. It is, however, 

 a true Pseudocuma, as shown by the structure of the several limbs. 



Description of the female. 



The largest specimens attain a length of nearly 6 mm.; but generally it 

 is far inferior in size, scarcely exceeding 4}/ 2 mm. 



The general form of the body (see figs. 1 and 2) is exceedingly slender and 

 elongated, more so even than in most other known Cumacea. The anterior di- 

 vision of the body appears, from this cause, to be less sharply marked off from 

 the posterior than in most other species, exhibiting a rather narrow oblong 

 form. As seen from above (fig. 1), it has its greatest breadth about in the middle, 

 and tapers very slightly, and quite uniformly, both anteriorly and posteriorly. 

 In a lateral view (fig. 2), it appears somewhat thicker in its anterior part 

 than posteriorly, and its upper contour forms a very slight and even curve. 



The carapace is comparatively small, not nearly attaining the length of 

 the exposed part of the trunk, and exhibits, as seen from the side (fig. 2), 

 a somewhat oval form, with the upper contour nearly straight, and the in- 

 ferior edges evenly curved. The branchial regions are but faintly marked 

 off from the adjacent parts of the carapace, and the gastric area exhibits 

 the usual bell-shaped aspect, terminating in front in a semicircular ocular 

 lobe. The pseudo-rostral projection is comparatively short, horizontal, and 

 somewhat obtuse at the tip. Below it is a slight sinus defining it from the 

 antero- lateral corners, which latter project but slightly, and are obtusely 

 rounded. 



The free segments of the mesosome are quite evenly vaulted above, 

 without any trace of keels or projections. The 2nd and 3rd segments are 

 considerably larger than the others, and have the epimera very broad and 

 laminar. The last segment is comparatively small, and has the epimera evenly 

 rounded. 



Bnllotin N. S. IV (XXXVI) p. 319. 



