On Fresh-water Crustacea. By Robert Gurney. 297 



be considered as distinct. "While the form of the body and of the 

 fifth feet in the female seem to agree exactly with those of D. 

 steindachneH, the prehensile antenna and the fifth feet of the 

 male present differences which are very striking. The description 

 given of D. drieschi is somewhat imperfect, but a comparison of 

 the fifth feet, in both sexes of the two species, seems to make 

 specific identity impossible. The relationship between D. numi- 

 dievs and D. steindachncri is very close, and they seem, together 

 with D. drieschi and D. vulgaris, to form a group of nearly con- 

 nected species. 



Diaptomus cyaneus sp. n. — Female : Body stout, the greatest 

 width being in the first free thoracic segment (plate XIII. fig. 35). 

 Last segment of the thorax with small lateral lobes pointed at 

 their outwardly directed apices and with a small posterior spine 

 (plate XIII. fig. 36). Rostral processes rudimentary. Abdomen 

 short, its length, including the furcal rami, equal to the greatest 

 width of the thorax. Genital segment scarcely dilated, with a 

 minute blunt spine on either side. A distiuct line of division 

 runs across the dorsal face of it, making the abdomen to consist of 

 five segments. Furcal rami about twice as long as broad, ciliated 

 on their inner edge and sometimes on the outer edge also. 



The antennas reach, when reflexed, as far as the last segment 

 of the thorax. 



Fifth pair of legs with the basal joint bearing a short broad 

 tooth (plate XIII. fig. 38). Endopodite two-jointed, the proximal 

 joint the shorter, equalling the first joint of the exopodite in length. 

 At its apex are two long slender spines of unequal length. Third 

 joint of the exopodite distinct though very small, bearing two 

 unequal spines. The egg-sacs contain very numerous small eggs, 

 as many as 60 or 70 being counted. 



Male: — Body tapering little anteriorly. Last segment of the 

 thorax symmetrical ; abdomen and furcal rami symmetrical. Last 

 segment of the prehensile antenna without a hook. Penultimate 

 joint with a small process one-third the length of the succeeding 

 joint (plate XIV. fig. 39). Hyaline membrane present, but very 

 narrow. The 14th, 15th, and 16th joints bear setae and sensory 

 rods only. 



Fifth pair of legs (plate XIII. fig. 37). — In the right leg the 

 basal joint bears a small hyaline membrane ; the endopodite is 

 slender, much longer than the first joint of the exopodite. Second 

 joint of the exopodite short and broad, the long lateral spine 

 inserted beyond the middle. In the left leg the second basal 

 joint has a small hyaline process. The endopodite is longer than 

 the first joint of the exopodite. Second joint of the latter forms a 

 rounded hairy pad on its inner surface, and is produced into a 

 finger-like process having a striated hyaline membrane on its 



