Plesiogammarus, Iphigeiiella 447 



setae, flagelliim 4-jointed. Gnathopods 1 and 2, 5*^ Joint short, 6^^ slenderly 

 oblong, in gnathopod 2 considerably larger than in gnathopod 1 and slightly 

 widening at the palm, wbich in both is much shorter than the bind margin. 

 Peraeopods 3 — 5, 2"^ Joint narrow, almost rod-like, a little wider above tban 

 below, 4 — 5 times as long as broad, witbout setae on bind margin, wbile 

 the 4^^^ and 6**^ joints of these limbs, the margins of peduncle in uropods 1 

 and 2 and the lateral surfaces of the pleon segments are beset with numerous 

 long setae. Uropod 1 reaching eud of uropod 3 or somewhat beyond. 

 Uropod 2 reaching scarcely % iength of uropod 3. Uropod 3 of \'j2 — Vio iength 

 of body, rami equal, beset with simple setae. Telson broader than long, divided 

 beyond the raiddle but not nearly to the base, lobes with numerous apical 

 setae. Colour yellow. L. reaching 16 mm. 



Lake Baikal. Depth 20—100 m. 



36. Gen. Iphigenella 0. Sars 



1896 Iphigenella (Sp. typ.: I. acanthopoda) {Iphigeneia 0. Grimm in MS.), G. O. 

 Sars in : Bull. Ac. St.-Petersb., ser. 5 ü. 4 p. 478. 



Body almost smooth, robust, pleon segments 4 and 5 with a few dorsal 

 hairs and a pair of subdorsal spinules, segment 6 with 2 pairs of spinules. 

 Side-plates rather lai-ge, not setiferous. Antenna 1 the longer, with accessory 

 flagellum. Mouth-parts nearly as in Gammarus (p. 460), but with inner lobes 

 indicated in lower lip. Gnathopod 1 with short 5*^ and large 6*^^ Joint. Gnathopod 2 

 with 5*^ and 6*^ Joints elongate, slender. Peraeopods 1 — 5 narrowly sub- 

 chelate. Peraeopods 3 — 5 rather short and stout, 2*^ Joint well expanded. 

 Uropod 3 not very large, outer ramus much longer than peduncle, 2-jointed, 

 inner ramus scale-like. Telson narrow, cleft to the base. 



1 species. 



1. I. acanthopoda 0. Sars 1896 I. a., G. O. Sars in: Bull. Ac. St.-Petersb., 

 ser. 5 vA p. 478 1. 12 f. 1—17. 



Body moderately compressed. Pleon segments 4 — 6 slightly cai-inate. 

 Head scarcely rosti-ate, lateral lobes obliquely ti-uncate. Side-plates 1 — 4 

 rather deep, 4*^ the largest, much deeper than broad, emarginate, 5*^ with 

 front and bind lobes subequal. Pleon segment 3, postero-lateral comers 

 acutely subquadrate. Eyes small, oval, dark. Antenna 1 more than ^j^ as 

 long as body, peduncle shorter than in antenna 2, 1^*^ Joint longer than 

 2*^ and 3* combined, flagellum twice as long as peduncle, 17-jointed, accessory 

 flagellum 4-jointed. Antenna 2 rather stouter, ultimate and penultimate 

 joints of peduncle subequal, flagellum little shorter than peduncle, 10-jointed. 

 Gnathopod 1, 5^^ Joint short, cup-shaped, 6*^ powerful, in-egularly oval, 

 widening to the rather oblique, sinuous palm, which is about equal to the bind 

 margin and has a streng spine near the middle and 2 at the obtusely rounded 

 palmar angle, iinger long and falciform. Gnathopod 2, 5*^ Joint long, a 

 little wider and shorter than the sublinear 6*^, both setose, palm transverse, 

 extremely short, finger to match. Peraeopods 1 and 2 alike, rather slender. 

 Peraeopods 3 — 5 subequal, shorter than peraeopods 1 and 2, 2<^ Joint in 

 peraeopods 3 and 4 quadrangular oval, widest above, in peraeopod 5 obliquely 

 expanded, produced below in a broadly rounded lobe. In all peraeopods the 

 6*^ Joint has a wide apex armed with stout spines, forming a kind of palm, 

 against which the short, strongly curved finger impinges. Uropods 1 and 2, 



