78 CRUSTACEA MALACOSTRACA III. 



female (fig. 2 b) the first joint is somewhat thick, the third minute, with a long sensory filament (j); 

 in the male (fig. 2 d) the antennulae are much thicker than in the other sex, the first joint very thick, 

 the two others with about six sensory filaments (s). - - The antennae are somewhat short (figs. 2 a and 

 2 c), reaching scarcely or about to the antero-lateral angles of third thoracic segment ; penultimate joint 

 of the peduncle conspicuously longer than the terminal; flagellum in the female (fig. 2 b) 4 or 5-jointed 

 and conspicuously less than half as long as the peduncle, in the male 5-jointed and about half as long 

 as the peduncle. - - Distal joints of the maxillipeds nearly as in M. spinifcra (comp. Sars, PI. 51). 



The thoracic segments decrease nearly gradually in breadth from the third to the seventh ; the 

 latter is about twice as broad as long; fourth about as long as or a little longer than the fifth, in the 

 female twice, in the male somewhat less than twice, as broad as long. The postero-lateral angles of 

 fourth to sixth segments subrectaugular or feebly produced; the posterior angles of these and of seventh 

 segment bear a minute spine. The ventral side of the three anterior segments is strongly carinate in 

 the median line; the keel of first segment is produced forwards as a long, almost horizontal process 

 projecting beyond the base of the maxillipeds; the keel of second and third segments without any 

 process. The four posterior segments with a median ventral keel, which is somewhat feeble on fourth 

 and fifth segments, but more developed on sixth and seventh ; the keel of each of these four segments 

 terminates at both ends without any process. 



The thoracic legs in the main as in M. spinifera. Third pair (fig. 2 e) have the dorsal spine on 

 third joint somewhat short and straight, the setae on the upper margin of fourth and fifth joints un- 

 usually long, not bifid at the end. Sixth pair (fig. 2 f) slightly longer than the seventh ; sixth joint 

 about two-thirds as long as the fifth and scarcely longer than the fourth; seventh joint considerably 

 less than half as long as the sixth and scarcely as long as the claw. 



Abdomen in both sexes only a little shorter than the sum of the three posterior thoracic seg- 

 ments, in the female (fig. 2 a) not fully half as long again as broad, somewhat broader before the 

 middle than at the insertions of the uropods, in the male distinctly more than half as long again as 

 broad, with the lateral margins nearly parallel (fig. 2 c); in both sexes the posterior part between the 

 uropods is considerably produced backwards, with each half of the margin slightly concave and the 

 end narrowly rounded. In both sexes the ventral excavation (figs. 2 g and 2 h) is uncommonly narrow, 

 leaving a comparatively broad area between itself and the lateral margin. - The female operculum 

 (fig. 2 g) is unusually small and short, terminating somewhat before the insertion of the uropods, oblong- 

 ovate, a little more than half as long again as broad, while the anal doors are situated midway between 

 the operculum and the end of abdomen. In the male (fig. 2 h) the operculum terminates considerably 

 before the insertion of the uropods, occupying only three-fifths of the length of the excavation; the 

 anal doors are nearer to the end of abdomen than to the operculum. - The uropods are two-jointed; 

 in both sexes the first joint is about as long as the sum of the abdomen and last thoracic segment, 

 straight, robust and tapering to the obliquely produced end (fig. 2 h); in a single male the second 

 joint has been preserved, and this joint, which is scarcely one-fourth as long as the first, is inserted 

 behind the oblique process and terminates in a few setae. 



Length of a female without marsupium 3-1 mm., of a female with marsupium 3 mm., of a male 

 2-4 mm. 



