CRUSTACEA MALACOSTRACA. III. 



II 9 



a little concave, taken as a whole considerably converging backwards, with the keels on most of the 

 surface very conspicuous; in the male this segment (fig. 5 c) is distinctly narrower than second or 

 third segment, scarcely twice as broad as long in the median line, with the anterior part of the lateral 

 margins feebly convex, their median part slightly concave, and the keels on the surface developed 

 only towards the lateral margins. -- Epimera subsimilar in both sexes; first to third pairs have their 

 anterior section produced as triangles as long as or a little longer than broad, and terminating in 

 spines, which are robust on first pair, thin on the two following pairs; fourth pair of epimera with 

 the produced part quite small. 



First pair of legs (fig. 5 d) with second to fourth joints robust, while the fifth joint is very 

 thick; this joint has the lower distal part somewhat produced as a foot for the very long and robust 

 spine, and its lower margin, which is a little less than twice as long as the depth of the joint, is 

 slightly concave and without any spine, but with only a couple of short setse and a moderately long- 

 seta just behind the base of the terminal spine. Sixth joint is slightly longer than the lower margin 

 of fifth joint, and about three times as long as deep. — Second pair of legs (fig. 5 e) rather slender; 

 fifth joint somewhat more than three times as long as deep, increasing a little in depth to beyond 

 the middle, with about nine slender spines, gradually increasing in length, along the lower margin, 

 and nine stiff setse in an oblique row on the outer side; sixth joint with slender spines, the two distal 

 very long, on the lower margin, and about four setse on the outer side towards the upper margin. - 

 Seventh pair (fig. 5 f) somewhat slender or moderately strong; fifth joint with four long setse on the 

 lower margin near its end; sixth joint with five or six long setse along the distal half of the 

 lower margin. 



Abdomen (fig. 5 a) a little longer than broad, tapering considerably from near the base to the 

 end, without postero-lateral teeth, and the posterior margin only a little convex. -- Operculum in the 

 female a little emarginate behind; in the male the pleopods of first pair have the lateral margins 

 nearly parallel to the rounded end. — Uropods (fig. 5 g) inserted only a little from the lateral margins ; 

 they are more than half as long as the abdomen, with the peduncle twice as long as broad, consider- 

 ably broader than, and a little more than half as long as, the slender endopod; exopod wanting. 



Length of a female with marsupium 3-1 mm., of a male 1-85 mm. 



Remarks. D. insigne, D. plebejum n. sp., and D. chelatum Stephensen constitute a group 

 within the genus Desmosoma, as the distal joints of the first pair of legs form a kind of chela, the 

 fifth joint being the hand, the strong spine answering to the immovable finger, while the sixth joint 

 is the movable finger, and the hand has no spines on the lower margin. (A fourth species of this tribe 

 is the antarctic Eugcrda longimana Vanhoffen, as its first pair of legs have similar chelse, but it dif- 

 fers from the three other species in possessing an exopod on the uropods, an additional proof that 

 the presence or absence of the exopod is less than valueless as a generic difference between Desmosoma 

 and Eugerda). It may be added that D. chelatum Stephensen, from off Elba in the Mediterranean, is 

 considerably larger than D. insigne, as the type, a female with marsupium, is 4-4 mm. long; some 

 characters between the two species are pointed out in the key (p. 109), and, besides, the second pair of 

 legs in D. chelatum have fourteen spines on the lower margin and end of the fifth joint, and twelve 



