Echinogammarus 491 



22. E. vittatus (Dyb.) 1874 Gammarus v., B. Dybowsky in: Horae Soc. ent. 

 Ross., u 10 suppl. p. 82 I 1899 Echinogammarus V., T. Stebbing in : Tr. Linn. Soc. London, 

 ser. 2 «7.7 p. 429 | 1893 Gammarus fluviatilis (part.)?, A. Della Valle in: F. Fl. Neapel, 

 r.20 p.931. 



Pleon Segment 1 with dorsal spines in a Single cross-row formed by 2 quite 

 small lateral groups and 2 middle spines, whicli seem to stand immediately 

 on the dorsal surface; segment 2 with 3 cross-rows, the front one composed of 

 2 middle groups, the next and the one on the hind margin of 2 middle 

 and 2 lateral groups, each containing 4 or 5 spines; segment 3 like segment 2, 

 but with addition in front of 2 little groups on the median liue; segment 4 

 with 2 cross-rows, the front one composed of 2 middle groups, the hinder of 2 

 middle and 2 lateral groups, having 2—5 spines in each; segments 5 and 

 6 each with 1 cross-row formed by 2 middle and 2 lateral groups. Eyes 

 moderately large, reniform, black. Antenna 1 not ^/o as long as body, 

 ^4 — V:< l*^nger than antenna 2, flagellum not twice as long as peduncle, 

 33 — 39-jointed, accessory flagellum 5- or G-jointed. Antenna 2, flagellum shorter 

 than peduncle. 12 — I5-jointed. Gnathopod 1, ö^'^ Joint slenderly piriform, 

 somewhat larger than oblong 6**" Joint of gnathopod 2. Peraeopods 3 — 5,*2<^ Joint 

 moderately broad, hind margin prolonged below in an obtuse angle, the margin 

 convex in peraeopod 3, a little sinuous in peraeopods 4 and 5. Uropod 1 

 reaching end of shorter ramüs of uropod 3. üropod 3 moderately long, 

 inner ramus % — ^/^ as long as outer, both fringed with uumerous fascicles 

 of setae, and both having among tiie simple setae of the fascicles on the inner 

 margin plumose setae. Colour bright yellow green, or bright olive-green, 

 each segment with a narrow stripe of brown on hind margin, antennae 

 brown, with narrow greenish bands. L. 23 mm. 



Lake Baikal. Under stones. 



23. E. petersii (Dyb.) 1874 Gammarus p., B. Dybowsky in: Horae Soc. ent. 

 Boss., V. 10 suppl. p. 83 t. 10 f. 1 I 1899 Echinogammarm p., T. Stebbing in: Tr. Linn. 

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

 F. Fl. Neapel, v. 20 p. 930. 



Peraeon segment 7 very rarely having a couple of delicate spinules 

 on the hind margin; pleon segments 1 — 6 each with 1 cross-row of dorsal 

 spines, on segments 1—3 forming 6 groups, 2 middle, 2 lateral and 2 

 marginal, on segments 4 — 6 ouly4 groups, 3 — 5 spines in a group; exceptionally 

 sonie delicate isolated dorsal spinules occur on segments 2 and 3. Head 

 with slightly convex upper outline. Eyes moderately large, reniform, a little 

 widened below and narrowed above, white, difficult to make out in spirit, 

 not darkening with exposure to light. Antenna 1 thrice as long as body, 

 5 times as long as antenna 2, extremely brittle, P* Joint stout, longer than 

 2*i and 3*^ combined, shorter than ultimate Joint of peduncle of antenna 2, 

 flagellum never found complete. 17 times as lon^ as peduncle, at least 

 350-jointed, accessory flagellum fully as long as peduncle, 16-jointed. 

 Antenna 2, ultimate Joint of peduncle slender, much longer than penultimate, 

 flagellum longer than peduncle, 27 — 57-jointed. Legs delicate. Gnathopod 1, 

 6*^*1 Joint piriform. Gnathopod 2, 6*^ Joint oblong. In figures gnathopod 1 

 in has the 6*'» Joint shorter, broader and with longer hind margin than 

 in d, and gnathopod 2 in d has the ^^^ widening to the palm much more 

 than in Q , and consequently with a longer palm and longer fingen Peraeopods 

 3 — 4 (5?), 2^ Joint moderately broad, hind margin little convex, ending 

 below with a weakly projecting angle; 2*^ Joint of peraeopod 5 (in figure) 

 naiTOw, its breadth greatest at top, equalling only % of its length, the 



