492 Echinogamniarus 



bind margin almost straight, ending below iu a little obtuse point. üropods 

 1 and 2 reaching end of shorter ramus of uropod 3. Uropod 3 long, inner 

 raraus about % as long as outer, of whieb the 2*^ Joint is well developed, 

 ^/, as long as 1^* Joint; both rami with plumose setae on both margins. 

 Colour delicate, clear violet or reddish white. L. about 29 mm. 

 Lake Baikal. Depth 700 -1300 m. 



24. E. violaeeus (Dyb.) 187-i Gammarus v. -\- G.v.var.virescens, ß. Dybowsky 

 in : Horae Soc. ent. Koss., v. 10 suppl. p. 75 1. 10 f . 3 ; p. 76 1. 12 f. 5 ; 1899 Echinogamniarus 

 violaeeus, T. Stebbing in: Tr. Linn. Soc. London, ser.2 v.l p. 429 | 1893 Gammarus 

 calcaratus (part.)?, A. Della Valle in: F. Fl. Neapel, f. 20 p. 931. 



Pleon Segments 1 — 6 each with 1 cross-vow of dorsal spines on the 

 bind margin pectinately set on ridge-like elevations in 2 middle groups 

 with 3 — 5 spines each, and 2 lateral groups with 4 — 7 spines each. Head, 

 rostral point short and rounded. Eyes small, reniform, slightly widened 

 below, black. Autenna 1 in d as long as body, raore than twice as long as 

 antenna 2, P*^ Joint not greatly longer than 2<^,'nor 2^ tlian 3*^, flagellum about 

 4 times.a8 lougaspeduncle, 91 — 148-joiuted. accessory flagellum 7- or 8-jointed. 

 Antenna 2, ultimate Joint of peduncle longer than penultimate, flagellum 

 shorter than peduncle, 18 — 25-jointed. Gnathopod 1, 6*^ Joint broad, piriform. 

 Gnathopod 2, 6**^ Joint slender, oblong. In figure gnathopod 1 has 5^'' Joint 

 as broad as long, 6*^ Joint twice as long as 5<^ broadly oblong oval; gnatho- 

 pod 2 has ö*'^ Joint long and narrow, not much shorter than the 6^^ the 2 conibined 

 being much longer than the much broader 5^'' and 6*^'» of gniitbopod 1 combined. 

 Peraeopods 3 — 5, 2** Joint broad, in peraeopod 5 beart-shaped, about 7:-, 

 longer than broad, bind margin convex, prolonged below into a short angle. 

 Uropods 1 and 2 short, reaching almost % length of uropod 3. uropod 3, 

 inner ramus about -/t — ^^ shorter than outer, with plumose setae on both 

 margins, wbile the outer ramus has them only on the inner. Colour dark 

 violet-red or brownish red, appeudages brightly banded. L. reaching 37 mm. — 

 Var. virescem distinguislied by smaller eyes, shorter uropod 3, broader 2*^ Joint 

 to peraeopods 3 — 5 and a smaller nuraber of spines. 



Lake Baikal. Depth 20—100 m. 



25. E. ibex (Dyb.) 1874 Gammarus i., B. Dybowsky in : Horae Soc. ent. Ross., 

 «;. 10 suppl. p. 78 I 1899 Echinogammarus i, T. Stebbing in: Tr. Linn. Soc. London, 

 ser.2 V.7 p. 429 | 1893 Gammarus fluviatUis (part.)?. A. Della Yalle in: F. FI. Neapel, 

 «;. 20 p. 929. 



Pleon Segments 1 — 6 each with 4 groups of dorsal spines on very 

 slight elevations of the bind margiu, the 2 middle groups with 1 — 3 spines 

 each, the lateral groups with 4 — 8. Head, frontal line almost straight. Eyes 

 large, broad, reniform, slightly widened below, not far apart above, black. 

 Antenna 1 longer than body, twice as long as antenna 2, 1^*^ Joint stout, shorter 

 than ultimate Joint of peduncle of autenna 2, flagellum 5 times as long as peduncle, 

 73 — 80-jointed, accessory flagellum 8-jointed. Antenna 2, flagellum shorter than 

 peduncle, 24— 30-jointed. Gnathopods 1 and 2, 6^^ Joint moderately large, in ö 

 slightly widening to the palm, in gnathopod 1 piriform, in gnathopod 2 oblong. 

 Legs delicate and tbin. Peraeopods 3 — 5, 2<^ Joint not broad, front margin 

 carrying long setae, the feebly convex bind margin 10—16 short setae, and 

 ending in a short projecting angle, üropods 1 and 2 long, but scarcely 

 reaching middle of uropod 3. Uropod 3 in d almost Vg as long as body, 

 outer ramus about Vg longer than inner, both having plumose setae on both 

 margins. Colour uniform yellow, or with horn-yellow markings. L. 14 mm. 



Lake Baikal. Depth 150—200 m. 



