508 Gammaracanthus, Acanthogammarus 



Uropod 3, rami fringed with plumose setae. Telson uearly twice as broad 

 as long, cleft wide, angular, more thau half the leogth. L. Q 35 mm. 



Sweden, Norway, Russia. Lakes. 



2. G. lorieatus (Sab.) 1821 & 24 Gammarus l, E. Sabine in: \V. E. Pariy, J. 

 Yoy., Suppl. p. 53 t. 1 f. 7; p. 231 t. 1 f. 7 | 1838 G.l, Kröyer in: Danske Selsk. Afh., 

 v.l p.250t.l f.4 I 1866 G.l, Goesin: Öfv. Ak. Förh., I/.22 p.531 | \Sid2 Gammaracanthusl, 

 Bäte, Cat. Amphip. Brit. Mus., p. 202 t. 36 f. 2 | 1876 G. l, A. Boeck, Skand. Arkt. 

 Amphip-, V.2 p.400 | 1894 (?. /., T. Stebbing in: Bijdr. Dierk., f. 17 p.40 | 1893 Ceradocusl, 

 A. Della Valle in: F. Fi. Neapel, u 20 p. 719. 



Near to G. lacustris (p. 507). Body rather stouter. Dorsal carina well deve- 

 loped from rostrum to pleou segment 5 inclusive, variably sbaped on the anterior 

 peraeon segments. Head, rostrum curved, projecting beyond 1^^ joiut of antenna 1, 

 lateral corners rounded, not very large, projection below boldly prominent. 

 Pleon Segments 2 and 3, lateral corners acutely produced. Eyes rather small, 

 oval reniform, dark. , Antenna 1, flagellum 30-jointed, accessory flagellum 

 4-joiuted. Antenna 2, flagellum 12 — 16-jointcd. Gnathopods 1 and 2 

 similar to those of G. lacustris, but more robust and gnathopod 2 decidedly 

 larger than gnathopod 1. Peraeopods 3—5 a little stronger than in G. lacustris. 

 Colouf yellowish white. L. reaching 43—58 mm. 



Arctic ücean (Greenland, Spitzbergen, Nova Zembla, Siberia). Deptli 79 m. 



3. G. caspius 0. Sais 1880 G. c. (nom. nud.). 0. Grimm in: Arcli. Naturg.. 

 «.46i p.ll9 I 1896 G.c, G. Sarsin: Bull. Ac. St.-Petersb., ser. 5 vA p.439 t.4 f. 1-6. 



Very like G. loriciitus, but rostrum nearly stiaight, only reaching 

 apex of 1^* Joint of antenna 1, projections below lateral corners of head less 

 prominent; pleon segments 2 and 3, postero-lateral corners less produced. 

 Antenna 2, flagellum shorter than ultimate Joint of peduncle, 8-jointed. 

 L. 36 mm. 



Caspian Sea. Depth 203 m. 



52. Gen. Acanlhogammarus Stebb. 



1899 Acavthogamrnarus, T. Stebbing in: Tr. Linn. Soc. London, ser. 2'i\7 p. 430. 



Body with median more or less dentate carina, and also lateral or 

 marginal carinae more or less developed. Head, rostrum very short. Side- 

 plate 5 much shallower than 4*''. Antenna 1 the longer, accessory flagellum 

 usually much developed. always with more than 1 Joint. Mouth-parts normal. 

 Peraeopods 3 and 4, 2*^ Joint narrowed below. Üropod 3, rami subequal, 

 not foliaceous. Telson deeply cleft. 



6 species. 



Synopsis of species: 



( Uropod 3, outer ramus shorter than inner — 2. 

 \ Uropod 3, outer ramus not shorter than inner — 3. 



j Peraeopod 5 shorter than the body I.A. cabanisii : . . . p. 509 



\ Peraeopod 5 longer than the body 2. A. zienkowiezii . . . p. 509 



1 Side-plates 1 — 4 with lower margin concave . 3. A. godleAArskii . . . . p. 510 

 ) Side-plates 1 — 4 with lower margin not concave — 4. 



I Side-plate 4 with oiitward projecting process 4. A. radoszkOAÄrskii . . p. 510 

 \ Side-plate 4 without outward projectingprocess — 5. 



f Median carina without denticles 5. A. armatus p. 511 



\ Median carina with denticles 6. A parasiticus . . . p. 511 



