400 Micniropus 



All Segments dorsally smooth. Side-plates 1 — 4 with setae. Eyes very 

 small, punctiform, black. Antenna 1 half as long as body, twicc as long as 

 antenna 2, longer tlian in other species of this genus, flagellum more than 

 twice as long as peduncle, 23-joiIited. Antenna 2, ulthnate Joint of pedüncle 

 sliorter than pemiltiraate. flagellum 9-jointed. Gnathopods 1 and 2, ß**! Joint 

 piriform, little larger in gnathopod 1 than in gnatliopod 2, palm very long 

 and oblique, tinger long, curved. Peraeopods 3 — 5, 2*^ Joint with uumerous 

 fascicles of setae at the strongly convex lower front corner, upper hindei* 

 part in peraeopods 3 and 4 with broad winglike expansion, bind margin with 

 long setae; peraeopod 5 very broad, evenly expanded behind. setose on both 

 margins. Uropods 1 and 2 reaching much beyoud uropod 3. üropod 3 very 

 Short, scarcely ^ao '^^ ^^^S ^^ body, outer ramus about twice as long as 

 inne]-, with 3 apical and 2 pairs of marginal spiues, inner with 2 marginal 

 spines and 1 or 2 apical setae. Telson liroacfei- than long, cleft to base, 

 lobes conical, divergent. L. about 20 mm. 



Lake Baikal. Dpi)th 2—10 m. 



3. M. vortex (Dyb.) 1874 Gammarusv., B. Dybowsky in: Horae Soc. ent. Jioss., 

 V. 10 suppl. p. 178 t. 9 f. 4 I 1899 Micruropus v., T. Stebbing in: Tr. Linn. Soe. London, 

 ser. 2 ». 7 p. 424 1893 Gammarus pungens (part.)?, A. Della Valle in: F. Fl. Neapel, 

 ».20 p. 931. 



Pleon Segments 4 — 6 with 3 groups of delicate dorsal spines and setae, 

 the number of setae small and variable ; other segments smooth. Side-plates 

 1 — 4 with isolated setae. Eyes of moderate size, reniform, black. Antenna 1 

 about ^3 3S long as body, a little longer than antenna 2, peduncle a little 

 shorter than peduncle of antenna 2, but in Q sometimes longer, flagellum 

 9 — 16-jointed. Antenna 2, flagellum with 5 — 9 joints, calceoliferous only in 

 the ö. Gnathopod 1, 6*'^ Joint piriform, as long as the oblong 6* Joint of 

 gnathopod 2, but (in figure) less bulky. Peraeopods 1 and 2, finger with 

 a strong spine on inner margin adjacent to the nail. Peraeopod 3, 2'^ Joint 

 slightly convex in front, the wing-like expansion produced somewhat down- 

 ward in a lobe-like rounded corner. Peraeopods 4 and 5, 2*^ Joint heai-t- 

 shaped, wide above, narrowed below, differing from the form usual in this 

 group, bind margin fringed with long setae. üropods 1 and 2 scarcely 

 reaching middle of uropod 3. Uropod 3 about Ve as long as body, therefore 

 rather distinct from rest of genus, outer ramus 2-jointed, inner only ^s or 

 ^j^ as long, both with plumose setae on inner margin. Telson cleft. Colour 

 greenish. L. ö 10, 9 6—7 mm. 



Lake Eaikal. Depth 5 — 30 m ; on stony coasts. 



4. M. talitroid.es (Dyb.) 1874 Gammarus f., B. Dybowsky in: Horae Soc. ent. 

 Boss., c.lO suppl. p. 47, 171 1. 14 f. 3 \ 1893 Atylus? t, A. Della Valle in: F. Fl. Neapel, 

 iJ.20 p. 930 1 1899 Micruropus t., T. Stebbing in: Tr. Linn. Soc. London, ser. 2 v.7 p. 424. 



Pleon Segments 5 and 6 with short, delicate, dorsal spinules, other 

 Segments smooth. Head, rostrum somewhat prominent, curved, bluntly 

 rounded. Side-plates 1 — 4 with setae. Eyes not large, reniform, brownish 

 Idack. Antenna 1 about 7« as long as body, about ^3 longer than antenna 2, 

 ))ut with rather shorter peduncle in d, flagellum 14 — 18-jointed. Antenna 2, 

 flagellum with 7 joints, calceoliferous only in ö. Gnathopod 1, 6*'» Joint rather 

 shorter and decidedly narrower than the oblong 6*'^ Joint of gnathopod 2, 

 described as piriform, but in flgure the palm is shorter than bind margin, 

 and, though very oblique, well defined. Peraeopods 3 and 4, 2*^ Joint with 

 convex, strongly setose, lower front corner, hinder expansion setose, rounded 



