On Fresh- water Crustacea. By Robert Gurney. 299 



of the thorax not completely fused with the preceding segment, 

 not greatly expanded laterally, but with its outer angles acute. 

 Abdomen of three segments only ; the genital segment more than 

 twice as long as the two succeeding segments tegether, bearing 

 on the left side anteriorly a short rounded knob and on either 

 side a long stout spine (plate XIV. fig. 42). These two spines 

 are not exactly symmetrical either in size or position. Second 

 segment of the abdomen very short, scarcely one-third of the 

 length of the third segment. Furcal rami broad, the breadth 

 greater than half the length, ciliated on both sides. Frontal fila- 

 ments absent. First pair of antenna? reach, when reflex ed, to the 

 end of the thorax. The fifth pair of legs (plate XIV. fig. 43) have 

 the endopodite slender, indistinctly two-jointed, nearly equalling 

 in length the first joint of the exopodite. The apex of it bears two 

 long seta? and a few small spines. Third joint of the exopodite 

 distinct, bearing two short, subequal spines. 



Male : Shape as in the female, but somewhat more slender and 

 tapering posteriorly. Third and fourth segments^of the abdomen pro- 

 duced asymmetrically on the right side (plate XIV. fig. 45). Pre- 

 hensile antenna? bears a stout spine on the fifteenth and sixteenth 

 joints, but no spine on the fourteenth. Penultimate joint with a 

 narrow hyaline lamella not produced at the distal end into a hook 

 (plate XIV. fig. 41). Terminal joint without a hook. Fifth pair 

 of legs (plate XIV. fig. 44). Eight leg has a large bilobed hyaline 

 lamella on the second basal joint. Endopodite short and club- 

 shaped ; second joint of the expodite with the lateral spine inserted 

 nearly in the middle, with a hyaline process at its base. Terminal 

 claw comparatively short and finely serrated. Left leg with endo- 

 podite cylindrical, 1-jointed, as long as the first joint of the exopo- 

 dite and bearing at the end two long seta?. Second joint of the 

 exopodite rather elongated, and with a hairy pad and short distal 

 spine ; inner spine, corresponding to the third joint, short and 

 stout. 



Length, female 5 to 5*5 mm. ; male, 4 to 4*5 mm. 



This very large species resembles in many respects Diaptomvs 

 roubaui Richard, but differs strikingly from it in some points. It 

 differs from it in the form of the genital segment, which in 

 D. roubaui is produced on the right side into a rounded process. 

 In the fifth foot of the female the spines of the third joint of the 

 exopodite are much shorter than in D. roubaui. and the endopodite 

 is a little longer. There is a considerable agreement in form 

 between the fifth feet of the male in the two species, but D. roubaui 

 lacks the hyaline membrane of the second basal joint of the right 

 foot and the long seta? of the endopodite of the left foot. The 

 abdomen of the male is exactly the same in both. 



My specimens were found in a pool at Oued Tindja. 



