486 Echiuogamiuarus 



slender, hind luargin slightly sinuous, Dot produced to an angle below. 

 üropod 1 reaches beyond middle of uropod 3. Tropod 3, outer ramus about 

 twice as long as inner, with plumose setae on the inner margin, 2"^ Joint 

 verj small, hidden among the long terminal spines. Colour yellowish, 

 playing into reddish. L. <5 9 — 15 mm. 



Lake Baikal. Depth 200 m. 



12. E. fuacus (Dyb.) 1874 Gammarus f., B. Dybowsky in: Horae Soc. ent. 

 ßoss., ».10 siippl. p. 63 t. 5 f. 2 I 1899 Echinogammarus f., T. Stebbing in: Tr. Linn. 

 Soc. London, ser. 2 v.l p. 429 | 18!»3 Gammarus fluviaülis (part.)?, A. Della Valle in: 

 F. Fl. Neapel, v. 20 p. 928. 



Pleon Segments 1 — 6 with dorsal spines in groups on slight elevations 

 of the liind margin; segments 1 and 2 with 2 middle and 2 lateral groups, 

 each with 4 spines; in all the segments the middle and lateral groups 

 sometimes unite on either side; segments 3 and 4 have an additional cross- 

 row of 2 groups, with variable number of spines. Pleon segments 1 and 2, 

 but not Segment 3, having the lateral lobe marked off. Eyes rather small, 

 reniform (in figure widened below), black. Antenna 1 about % as long as 

 body, only a little longer than antenna 2, 1^* Joint longer than 2*^ and 3'^ 

 combined, as long as ultimate Joint of peduncle of antenna 2 (in figure; shorter in 

 text). flagellum 30-jointed, accessory flngellum 7-jointed. Antenna 2, flagellum 

 20-jointed, with calceoli. Gnathopods 1 and 2, G^^ Joint moderately large, 

 in gnathoped 1 piriform, in gnathopod 2 rather smaller, oblong, but with 

 the palm rather oblique. Peraeopods 3 — 5, 2^ Joint rather broad, hind 

 margin convex or somewhat sinuous, ending below in a short, acutely 

 projecting point. Uropods 1 and 2 reaching middle of uropod 3. üropod 3, 

 inner ramus ^j^~'L as long as outer, both with simple setae on outer margin, 

 but also plumose setae on inner; 2*^ Joint of outer ramus (in figure) distinct. 

 Telson (in figure) with the lobes narrow, each having 3 spines at apex. 

 Colour violet-brownish, with greenish spots; hind margin of head and front 

 half of peraeon segment 1 brighter coloured; appendages banded. L. ö 

 reaching 39 mm. 



Lake Baikal. Depth 30—100 m. 



13. E. murinus (Dyb.) 1874 Gammarus tri., B. Dybowsky in: Horae Soc. ent. 

 Ross., «;. 10 snppl. p. 64 t. 5 f. 1 | 1899 Echinogammarus m., T. Stebbing in: Tr. Linn. 

 Soc. London, ser. 2 v.l p. 429 | 1893 Gammarus fluviatilis (part.)?, A.- Della Valle in: 

 F. Fl. Neapel, v. 20 p. 929. 



Pleon segments 1 — 6 with dorsal spines on low elevations of the 

 hind margin; segment 1 with 1 cross-row of 2 middle and 2 lateral groups, 

 each containing 4 or 5 spines; segment 2 with 3 cross-rows, the hindmost as 

 in segment 1, but here with 4 spines to a group, preceding row similar or with 

 only 2 middle ' groups, and the other row generally with only 2 middle 

 groups, spines varying from 1 — 3 in a group; segment 3 like segment 2, 

 but often with the addition of solitary spinules and simple setae; segment 4 

 with 2 cross-rows, the spines more delicate, and often giving place to setae; 

 segments 5 and 6 each with 1 cross-row, the lateral groups usually having 

 4 spines. the median 1 or 2 pairs of setae. Pleon segments 1 — 3 having 

 the lateral lobes distinctly marked off. Eyes rather large. reniform, widened 

 below and little rounded off, black. Antenna 1 nearly -/s »s long as body, 

 1^* Joint as long as 2^ and 3*^ combined, and as long as ultimate Joint 

 of peduncle of antenna 2, flagellum with 39 — 53 joints in 9 , 57 in d, 



