Acanthogammarus 509 



1. A. cabanisii (üyb.) 1874 Gammarus c, B. Dybowsky in: Horae Soc. ent. 

 Koss., V. 10 suppl. p. 122 t. 13 f. 5 | 1899 Acanthogammarus c, T. Stebbing in: Tr. Linn. 

 Soc. London, ser. 2 v.l p. 430 | 1893 Palldsea CQncellus (pait.)?, A. Della Valle in: F. 

 Fl. Neapel, v. 20 p. 928. 



Median carina on all segments, on peraeon segments 1 — 5 in the fonn 

 of low, naiTOW, tooth-like processes, looking in side-view like little triangles, 

 on peraeon segments 6 and 7 and pleon segments 1 — 3 in form of acute, 

 backward directed divided spines or of narrow, tolerably acute, and high 

 2-jointed teeth; all segments have also a flat, distinct marginal swelling, 

 and the pleon segments also on the bind margin a hump, carrying 1 or 2 

 spines. Head smooth above, not inflated in the ocular region, rostrum 

 acute, slightly directed upward. separated by a deep cavity fi'om the lateral 

 lobes. Side-plates 1 — 4 distally acute, the 1^* almost spine-like, greatly 

 advanced forward over the cheeks. Eyes small, point-like, white. Antenna 1 

 longer than the body, 4 — 6 times as long as antenna 2, 1^* Joint prismatic, 

 tapering, much longer than 2*^ and 3*^ combined, twice as long as ultimate 

 Joint of peduncle iu antenna 2, flagellum very long, 84 — 108-jointed, accessory 

 flagellum 8-jointed. Antenna 2, ultimate Joint of peduncle serrato-dentate 

 on inner margin, flagellum tapering, with 17 joints set obliquely, of serrate 

 appearance and furnished (?) with calceoli. Gnathopods 1 and 2, 6*^ Joint 

 is described as piriform, with broad base (in flgure rather oblong oval, with 

 no palm distinguishable). Peraeopods 3 — 5, 2^ Joint nearly thrice as long 

 as broad, almost linear, with the wing slightly developed above. Peraeopods 



4 and 5 shorter than the body. üropod 1 reaching much beyond uropod 3. 

 üropod 3, outer ramus about V? shorter than the inner, both having numerous 

 plumose setae. Telson cleft to the middle, apices acute (in figure blunt). 

 Colour white. L. 55 mm. 



Lake Baikal. Depth 200—700 m. 



2. A. zienkowiezii (Dyb.) 1874 Gammarus z., B. Dybowsky in: Horae Soc. 

 ent. Eoss., v.lO suppl. p. 124 t. 3 f. 5 | 1899 Acanthogammarus z., T. Stebbing in: Tr. 

 Linn. Soc. London, ser. 2 v.l p. 430 j 1893 Ceraäocus? zienkoviczii, A. Della Valle in: 

 F.Fl. Neapel, ».20 p.931. 



Median carina more or less strongly developed throughout peraeon and 

 pleon, on peraeon segment 1 as a hump with 3 teeth, 2 side by side bending 

 forward in front, a 3*^ behind bending back; on peraeon segments 2 — 6 

 commonly as a ridge with blunt hump in front and acute, forward bent tooth 

 behind; on pleon segments 1 — 3 the carina is higher, and has a 3^, acute, 

 straight tooth; on segment 4 there is a hump and a straight tooth, ou segments 



5 and 6 usually no tooth; on peraeon segments 1 — 5 the margins are swollen; 

 on all *the others, on the hind^ margin over the marginal swellings, there 

 is a hump which runs out into an acute, outward and backward directed 

 tooth. Head smooth, rostrum short, acute. Side-plates 1 — 4 shallow, 

 jst — 3d distally narrowed (not in figure) and rounded; 4*^ broad, the bind 

 emargination (in flgure) extending the whole depth of the plate. Eyes small, 

 point-like, violet. Antenna 1 nearly twice as long as body and seven times 

 as long as antenna 2, 1^* Joint as in A. cabanisii, flagellum of great length, 

 108 — 119-jointed, accessory flagellum 5-jointed. Antenna 2, ultimate Joint 

 of peduncle thickened, projecting over base of flagellum and armed with 

 long stout plumose setae, flagellum 7-jointed. Gnathopod 1, 6*^ Joint piriform. 

 Gnathopod 2 somewhat larger, 6*"^ Joint oblong, bind margin and palm convex. 

 Peraeopods 3 — 5 very long and fragile, 2^ Joint almost linear. Peraeopods 

 4 and 5 longer than the body. üropod 3, outer ramus about Vio shorter 



