Gammarus 475 



26. G. delebecquei Chevreux & Guerne 1892 G. d., Chevreiix & Guerue in: 

 Bull. Soc. zool. France, v. 17 p. 136 | 1893 G. fluviatilis (part.), A. Della Valle in: F. Fl. 

 Neapel, v. 20 p. 889. 



Geueral form of bodv, armature of pleon segments 4—6, postero- 

 lateral corners in segments 2 and 3 as in G. pulex. Eyes much larger, 

 faintly reniform. Antenna 1 more than half as long as body, flagellum 32 — 35- 

 jointed, more than twice as long as peduucle, accessory flagellum 4-jointed. 

 Antenna 2 shorter than P*, but more slender and elongate than in G. pulex, 

 flagellum shorter than ultimate and penultimate joiuts of peduncle combined, 

 12-jointed, with setae of uniform length. Gnathopods 1 and 2 as in G. pulex, but 

 with 6*^ Joint a little uarrower, and peraeopods 1 — 5 rather more slender. Peraeo- 

 pods 4 and 5, 2^ Joint with sinuous bind margin, rather abruptly narrowiug 

 distally. üropod 3, rami more sparsely fringed with setae, the outer with 

 .several groups of spines ou outer margiu. the inner slender, not more than 

 half as long as the P* Joint of outer. Telson apparentlv as in G. pulex. 

 L. Q 8, d 12 mm. 



France (from a warm spring at the bottom of the Lac d'Annecy). 



27. G. hyaeinthinus Dyl>. 1874 G. h., H. Dybowsky in: Horae Soc. ent. Ross., 

 r. 10 snppl. i).70 | 1893 G. fluviatilis (part.)'?, A. Della Valle in: F. Fl. Neapel, t).20 p.929. 



Pleon segments 4 — 6 each with dorsal spinules in 4 groups of 1. 2 

 m 3 a-piece. Eyes rather large, reniform, black. Antenna 1 not half as long 

 as body, flagellum thrice as long as peduncle, 28-jointed, accessory flagellum 

 4-jointed. Antenna 2 -^/^ as long as antenna 1. flagellum 15-jointed. Gnatho- 

 pods 1 and 2 not large, 6*'^ Joint in gnathopod 1 pii'iform, rather longer 

 than the oblong 6**" Joint in gnatliopod 2. Peraeopods 3 — 5. 2*^ Joint tolerably 

 broad, front and bind margins convex, the bind one ending below in a pointed 

 Corner, üropods 1 and 2 reaching "'.^ length of uropod 3. Uropod 3 not 

 very long, outer raraus with plumose setae only on the inner margin, inner 

 about ■* n as long as oiiter, with plumose setae on botli margius. Colour vaiiable, 

 greenish, yellowisli, or bright reddish. L. 15 mm. 



Lake Baikal. Depth 100—300 m. 



28. G. syriacus Chevrenx 1895 G. s., Chevreiix in: Rev. biol. Nord France, 

 V. 7 p. 160 f. 



Body ratlier robust. Pleon segments 1—3 with some stiff dorsal setae, 

 segments 4 — 6 each with a transverse elevation of bind margin armed with 

 a variable number of spines, usually 2 median and 1 on each side in segments 4 

 and 5, and only 1 on eacli side in segment 6; the spines accompanied by 

 setae. Head, lateral lobes vertically truncate, the sinus below smaller 

 than usual. Side-plates 1 — 4 deep, 4^*' much deeper than broad. Pleon 

 segments 1 — 3, postero-lateral corners acutely and uncinately produced, chiefly 

 in segment 3. Eyes of moderate size, reniform. Antenna 1 in d more than 

 half as long as body. flagellum feebly armed, more than twice as long as 

 peduncle, 40-jointed (21-jointed in Q ), accessory flagellum 4-jointed. Antenna 2 

 considerably shortei', ultimate Joint of peduncle rather longer than penultimate, 

 flagellum about 14-jointed, apparently without calceoli. Gnathopods 1 and 2 

 as in G. pulex. Peraeopods 1 and 2 with fascicles of long setae on bind margin. 

 Peraeopods 3 — 5 robust, not elongate, 2^ Joint in peraeopod 3 with lower bind 

 Corner quadrate, in peraeopods 4 and 5 bind coruer not free. Uropod 3, outer 

 ramus fringed on outer margin with long plumose setae, inner ramus over 

 "/g as long as outer, with 1 or 2 spines and a fringe of short plumose setae 



