Heterogammarus 49& 



Pleon Segments 4 — 6 with few, delicate spines on bind margin, other 

 Segments without dorsal armatuve. Head, rostrum obsolete. Eyes not large, 

 little prominent, reniform, black. Antenna 1 half as long as body, twice 

 as long as antenna 2, peduncle not thicker and very little longer than 

 peduncle of antenna 2, flagellum 46 — 50-jointed, accessory flagellum 7- or 

 8-jointed. Antenna 2, flagellum not longer than ultimate Joint of peduncle, 

 10- or 11-jointed. Gnathopods 1 and 2 in ö. 6^^ Joint piriform, in o that 

 of gnathopod l piriform, that of gnathopod 2 oblong, apparently the difference 

 of size being slight, and the palm in all cases very oblique. Peraeopods 3 — 5, 

 2^ Joint heart-shaped, bind margin of wing carrying a few short setae, and 

 ending below without forming a free corner, üropods 1 and 2 reaching 

 almost the middle of uropod 3. üropod 3 V? — Ve ^^ ^^^S ^^ body, inner 

 ramus nearly as long as outer, both fringed with numerous plumose setae. 

 Colour olive-green or brownish, with delicate brown or dark red markings. 

 L. 41 — 46 mm. — Vor. sclrtes is distinguished especially by the liveliness of 

 its Walking and hopping. L. 12"o mm. 



Lake Eaikal. Depth 1 — 50 m; on sandy coasts. 



3. H. capellus (Dyb.) 1874 Gammarns c, B. Dybowsky in: Horae Soc. ent. 

 Koss., ?;. 10 suppl. p. 100 | 1899 Heterogammarus c, T. Stebbing in: Tr. Linn. Soc. 

 London, ser. 2 v.7 p. 429 | 1893 Gammarus fluviatilis (part.)?, A. Della Valle in: F.Fl. 

 Neapel, v. 20 p. 928. 



Pleon Segments 4 — 6 usually with 3 little gi'oups of spines on the 

 bind margin, 1 or 2 spines in each group, other segments without dorsal armature. 

 Head, rostrum a feeble point. Eyes slightly prominent, renifonn, black. 

 Antenna 1 rather longer than the body, 4 times as long as antenna 2, 

 peduncle stouter and longer than peduncle of antenna 2, flagellum 46 — 52- 

 jointed, accessory flagellum 4-jointed. Antenna 2, flagellum 8- or 9-jointed. 

 Gnathopod 1, 6*^ Joint slenderly piriform, equal to the oblong 6*^ Joint of 

 gnathopod 2. Peraeopods 3 — 5, 2*^ Joint narrow, heai-t-shaped. Uropod 1 

 reaching middle of uropod 3, m-opod 2 scarcely reaching end of peduncle 

 of uropod 3. üropod 3 about ^s as long as body, inner ramus about -/s 

 as long as outer, both fiinged with plumose setae. Colour reddish yeUow with 

 scattered reddish brown spots. L. about 13 mm. 



Lake Baikal. Depth 100 m. 



4. H. ignotus (Dyb.) 1874 Gammarus i., B. Dybowsky in: Horae Soc. ent. 

 Ross., V. 10 suppl. p. 109 t. 4 f. 3 [ 1899 Heterogammarus i., T. Stebbing in: Tr. Linn. 

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

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



Surface of body dorsally hairy or caiTying scattered, short setae; only 

 on bind margin of. pleon segments 4 — 6 there are somewhat longer and 

 stouter setae. Eyes punctiform, white, in spirit not visible. Antenna 1 

 longer than half the body, fully twice as long as antenna 2, peduncle longer 

 than peduncle of antenna 2, flagellum 24-jointed, accessory flagellum 3-jointed. 

 Antenna 2, ultimate and penultimate joints of peduncle subequal, flagellum 

 9- or 10-jointed. Gnathopod 1, 6*^ Joint pirifonn, broader but shorter than the 

 nan-owly oblong 6*^ Joint of gnathopod 2; 5**^ Joint also shoi-ter in gnathopod 1. 

 Peraeopods 3 — 5, 2* Joint narrow, the wing in no part broad, distally almost 

 evanescent. Uropod 1 reaching nearly middle of uropod 3. Uropod 3 ^/^ 

 as long as body, outer ramus with 2*^ Joint well developed, inner about ^/^ 

 as long as outer, both with isolated simple setae, but without plumose setae. 

 Colour white. L. about 10 mm. 



Lake Baikal. Depth 800 m. 



