494 Heterogammarus 



47. Gen. Heterogammarus Stebb. 



1899 Heterogammarus, T. Stebbing in: Tr. Linn. Soc, London, ser. 2 v.7 p. 429. 



In general like Gammarus (p. 460), witliout dorsal teeth or carinae, or 

 notable processes of head or side-plate 1, with accessory flagellum of antenna 1 

 more than 1-jointed, uropod 3, outer ramus with 2 joints, and telson clefl; 

 but separated from Gammarus by one or more of the following characters: 

 peduncle of antenna 1 longer than peduncle of antenna 2, 6*^ Joint of gnatho- 

 pod 1 larger than 6*^ Joint of gnathopod 2, uropod 1 very short. 



8 species. 



Synopsis of species: 



J Uropod 3 long, ^|^ — Y* ^^ long as body — 2. 



\ Uropod 3 not long, ^jn — '/lo as long as body — 5. 



j Antenna 1 shorter than antenna 2 1. H. stanislavii. . p. 494 



\ Antenna 1 longer than antenna 2 — 3. 



/ Peraeopod 5, 2d joint witli well developed wing . 2. H. sophianosii . p. 494 



\ Peraeopod 5, 2djoint with wing scarcely developed — 4. 



{ 



. Uropod 3, inner ramus about ^/s as long as outer 3. H. capellus . . . p. 495 

 Uropod 3, inner ramus scarcely ^4 ^^ loßg as outer 4. H. ignotus . . . p. 495 

 Gnathopod 1, 6th Joint larger than that of 

 gnathopod 2 — 6. 



\ Gnathopod 1, öth Joint subequal to that of 



I irn 



gnathopod 2—7 

 J Peraeopods 3 and 4, 2d joint broad 5. H. flori . . . . p. 496 



Peraeopods 3 and 4, 2d joint narrow H.H. albulus . . . p. 496 



Antenna 1 half as long as body 7. H. bifasciatus . p. 496 



Antenna 1 ^ji as long as body 8. H. branchialis . p. 497 



1. H. stanislavii (Dyb.) 1874 Gammarus s., B. Dybowsky in: Horae Soc. ent. 

 ßoss., V. 10 suppl. p. 58 1 1899 Heterogammarus 8., T. Stebbing in: Tr. Linn. Soc. London, 

 ser. 2 v.7 p. 429 j 1893 Gammarus stanislavi, G. pungens (part.)?, A. Della Valle in: 

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



Juv. Only pleon segmeuts 4 — 6 carrying spines, these situated on 3 

 slight elevations of the hiud margin, the median with 2 or 3, the lateral each with 

 1 or 2 spines. Head, rostrum obsolete. Side-plates small and low. Pleon 

 Segments 2 and 3, postero-lateral comers acute. Eyes broadly reniform, 

 slightly widened below, black. Antenna 1 only about ^/^ as long as antenna 2, 

 peduncle shorter and thinner than peduncle of antenna 2, flagellum 25-jointed, 

 accessory flagellum 5- or 6-jointed. Antenna 2 about half as long as body, 

 flagellum 53-jointed. Gnathopod 1, 6*^ joint piriform, widened at base, larger 

 than 6*^^ joint of gnathopod 2, which is also piriform, but not specially widened at 

 base. Peraeopods 3 — 5, 2*^ joint rather slender, somewhat expanded proximally. 

 Uropod 1 reaching beyond uropod 2, to the end of inner ramus of uropod 3. 

 Uropod 3 long, ^4 ^s long as body, outer ramus 4 or 5 times as long as 

 inner, with plumose setae only on inner margin, inner ramus having them 

 on both margins. Colour bright reddish yellow. L. 18 — 20 mm. 



Lake Baikal. Depth 100 m. 



2. H. sophianosii (Dyb.) 1874 Gammarus s. + G. s. var. scirtes, B. Dybowsky 

 in: Horae Soc. ent. Ross., v. 10 suppl. p. 101 1. 10 f. 4; p. 102 t. 11 f . 2 | 1899 Hetero- 

 gammarus sophianosii, T. Stebbing in: Tr. Linn. Soc. London^ ser. 2 v.7 p. 429 ] 1893 

 Gammarus fluviatilis (part.)?, A. Della Valle in: F. Fl. Neapel, ».20 p. 930. 



