404 Micruropus, Neoiiiphargiis 



with only 1 very long apical seta, Telson divided. Coloiir greyish white. 

 L. about lU mm. 



Lake Baikal. Close to the shore. 



12. M. pachytus (Dyb.) 187-1 Gammarusp. -)- G.p. var. dilatatus, B. Dybowsky 

 in: Horae Soc. ent. Ross., ^^ 10 suppl. p. 182; p. 183 | 1893 Atylus? p., A. Della Valle 

 in: F. Fl. Neapel, v.20 p. 929 | 1899 Micruropus p., T. Stebbing in: Tr. Linn. Soc. 

 London, ser. 2 v. 7 p. 424. 



Segments smooth, except that the hind margin is thickened and overlaps 

 front margin of following segment. In var. dilatatus the surface of the 

 body covered with short hairs, and the setae of side-plates 1 — 4 long, 

 stout, almost spine-like. Eyes small, rounded reuiform, black. Antenna 1 

 ^/g as long as body, subequal to antenna 2, 1^* Joint hroad, flagellum 

 11-jointed, with oblique attachment, so that it is always directed outwards, 

 accessory flagellum 1-jointed. Antemia 2, flagellum 8- or 9-jointed. Gnatho- 

 pods 1 and 2 almost equally long, 6^^' Joint narrowly piriform in gnatho- 

 pod 1, obliquely oblong in gnathopod 2, in the var. gnathopod 1 is said to 

 be the larger. Peraeopods 3 — 5, 2*^ Joint very setose on hind margin. Peraeo- 

 pods 3 and 4, 2*^ Joint broader below than above (in var. considerably broader 

 above than below). Peraeopod 5, 2*^ Joint broad, strongly and evenly curved 

 behind, broadest in the upper half (in var. ti*apezoidal, broader below than 

 above). üropod 1 reaching at least as far back as uropod 3. üropod 3 

 very short, scarcely ^/jg as long as body, (in var. rudimentary, V25 ^s long 

 as body), outer ramus 2-jointed, less than twice as long as inner, with 

 3 spines on apex, 2 or 3 on outer margin (in var. with 4 on apex, 1 on 

 outer margin); inner ramus with 1 apical spine. Telson divided (in var. 

 Short, divided almost to the middle). Colour greyish white (in var. greenish 

 white). L. 15 mm. 



Lake Baikal. Depth 2 — 10 m. 



20. Gen. Neoniphargns Stebb. 



1899 Neoniphargns (Sp. typ.: N. thomsoni), T. Stebbing in: Tr. Linn. Soc. London, 

 ser. 2 u 7 p. 424. 



Side-plates 1 — 4 mnch deeper than those which follow. Eyes well 

 developed. Antenna 1 the longer. accessory flagellum very small, 2-jointed. 

 Mouth-parts nearly as in Niphargus (p. 405), but maxilla 1 said to have 

 6 spines on outer plate. Gnathopods 1 and 2 similar, subchelate, 5*^ Joint 

 distally wide, 6* quadrate. Peraeopod ö shortcr than peraeopod 4. üropod 3 

 not elongate, outer ramus 1-jointed, inner minutc. Telson partly cleft. 



1 accepted and 1 doubtful species. 



1. N. thomsoni Stebb. 1893 Niphargus montanus (non Gammarus m. A. Costa 

 1851!), a. M. Thomson in: P. R. Soc. Tasmania. 1892 p. 70 t. 6 f. 1—13 | 1899 Nemi- 

 phargus thomsoni, T. Stebbing in: Tr. Linn. Soc. London, ser. 2 v.7 p. 425. 



Head, lateral corners very little prominent. Side-plat» 1 rounded below, 

 4**1 broad, emarginate. Pleon Segments 1 — 3, postero-lateral corners rounded. 

 Eyes relativ ely large, subreniform, close to lateral margin of head. Antenna 1 

 Short. 2^ Joint rather shorter than 1^*, and 3*^ than 2^, flagellum rather longer 

 than peduncle, with about 14 joints, accessory flagellum rather longer than 

 1*»* Joint of primary. Antenna 2 said to be about half as long as antenna 1, 

 flagellum shorter than peduncle, 8-joiuted. Gnathopods 1 and 2, 5*^joint triangulär, 



