496 Heterogamraarus 



5. H. flori (Dyb.) 1874 Gammarus f., G. florü, B. Dybowsky in: Horae Soc. 

 ent. ßoss., «;. lOsuppl. p. 20, 52; 54, 188 | 1899 Heterogammarus flori, T. Stebbing in: Tr. 

 Linu. Soc. London, ser. 2 v.l p. 429 ] 1898 Gammarus fluviat'dis (part.)?, A. Deila Yalle 

 in: F. Fl. Neapel, tj. 20 p. 928. 



Pleon Segments 3 and 4 with dorsal fascicles of long setae, Segments 5 

 and 6 eacb with 4 or 5 groups of spines, usually 5 spines in each of the 

 oblique lateral gi'oups. Eyes white, in general roundish, small, in spirit not 

 visible. Antenna 1 -4 as long as body, less than twice as long as antenna 2, 

 peduncle subequal to that of antenna 2, its P* Joint with only a couple 

 of Short setae on front end, flagellum 22 — 27-jointed, accessory flagellum 

 3-jointed. Antenna 2, flagellum 7- or 8-joiuted. Side-plates low, with 

 1 or 2 marginal setae. Gnathopod 1, 6*^ Joint broadly oblong, larger than 

 the narrowly oblong 6*^' Joint of gnathopod 2. Peraeopods 3 and 4, 2^ Joint 

 about ^/g longer than broad, bind margin slightly sinuous, with short setae 

 in peraeopod 3, long, separate setae in peraeopod 4. Peraeopod 5, 2^ Joint 

 widened below and produced far downward in a rounded lobe, bind margin 

 with close set setae. Uropods 1 and 2 not reaching end of short uropod 3. 

 üropod 3 ^/j3 as long as body, inner ramus about ^/g as long as outer, 

 with simple setae on inner margin, outer ramus with them on both margius, 

 each ramus with 4 or 5 apical setae, neither with plumose setae. Colour 

 white. L. nearly 16 mm. 



Lake Baikal. Depth 50—100 m. 



6. H. albulus (Dyb.) 1874 Gammarus flori var. alhula, B. Dybowsky in: Horae 

 Soc. ent. Boss., v. 10 suppl. p. 53 |'1899 Heterogammarus albulus, T. Stebbing in: Tr. 

 Linn. Soc. London, ser. 2 t;. 7 p. 429. 



Peraeon Segments and pleon segments 1 — 3 each with 3 groups of 

 spines, 2 spines in the centre group, 3 in each of the oblique lateral groups. 

 Side-plates far lower, pleon segments 4 — 6 shorter, legs with broader joints 

 than in H. flori; eyes as in that species. Antenna 1 longer than half the 

 body, less than twice as long as antenna 2, peduncle stouter and rather 

 shorter than peduncle of antenna 2, its P* Joint with several strong spines on 

 front end, flagellum 16 — 24-jointed, accessory flagellum 3- or 4-jointed, shorter 

 than in H. flori. Antenna 2, flagellum 6 — 8-jointed. Gnathopods 1 and 2, 

 6^^^ Joint oblong, in gnathopod 1 larger than in gnathopod 2, and cousiderably 

 larger than in gnathopod 1 of H. flori, with 5 or 6 long spines along the 

 palm and 3 still longer on the bind margin. Peraeopod 3, 2^ Joint twice 

 as long as broad, bind margin feebly convex, without setae. Peraeopod 4, 

 2"^ Joint 27» as long as broad, bind and front margin close set with long 

 setae. Peraeopod 5, 2*^ Joint much narrower above than below, produced 

 far downward in a rounded lobe, üropods 1 and 2 short, but reaching 

 beyond uropod 3. Uropod 3 7io ^^ ^^^o ^^ body, inner ramus about % 

 as long as outer, carrying simple setae only at apex, outer having such 

 also on its outer margin. Colour white. L. o 8 mm, d 13 mm. 



Lake Baikal. Depth 300 m. 



7. H. bifasciatus (Dyb.) 1874 Gammarus b., B. Dybowsky in: Horae Soc. 

 «nt. Ross., V. 10 suppl. p. 102 t. 12 f. 6 | 1899 Heterogammarus b., T. Stebbing in: Tr. 

 Linn. Soc London, ser. 2 v.7 p. 429 | 1893 Gammarus fluviatilis (part.)?, A. Della Valle 

 in: F. Fl. Neapel, u 20 p. 927. 



Pleon segments 4 — 6 each with 2 groups of spinules. Head, rostrum 

 represented by a projecting cm've. Eyes not very large, slightly prominent, 

 reniform, ash-grey. Antenna 1 half as long as body, 2 or 3 times as long 



