Micruropus 401 



above, narrowed below. l'craoopod 5, 2*^ Joint setoso as in preceding peraeo- 

 pods, but longcr aiid soiuewhat l)roador, hinder expansiou narrower thau 

 nmscle-beariug part. Uropod 1 roacliing ond of uropod 3. Uropod 3 ^/j, — ^12 

 as long as body, outer ramus 1-jointod, % — % louger tliau inner, with 

 2 pairs of stroug spines on outer miu-giu, both rami liaviug long apical setae. 

 Telson cleft to base, each half (in figure) with 3 apical spinules. Oolour 

 yellowish or greeuish grey; front margin of head and side-plates 1 — 3, side- 

 plate 4, 2'^ Joint of peraeopods 3 — 5, uropod 3 and tolson, brownish blaok. 

 L. 11 mm. 



Lake Baikal. 



5. M. littoralis (Dyb.) 1874 Gammarus L, B. Dybowsky in: Horae Soc. ent. 

 Ross., V. 10 suppl. |). 168 t. 14 f. 2 j 1893 Atyhis? L, A. DellaValle in: F. Fl. Neapel, 

 ».20 j). 929 : 1899 Micruropus l., T. Stebhing in: Tr. Linn. Soe. London, ser. 2 v.7 p.424. 



Peraeon segraents 6 and 7 and ploon «egments 1 — 3 with dorsal setae, 

 pleon Segments 4 — 6 with groups of delicate spines arranged on upper curvature 

 of the Segments. Head, rostrum obtusely pointod. Hide-plates 1 — 4 with few 

 marginal setae. Eyes small, rounded reniform, wide apart, black. Antenua 1 

 (usually) shorter and with shorter peduncle than antenna 2, scarcely ^/^ as 

 long as body, l''*^ Joint stout, longer than 2'^ and 3*^ combined, flagellum 

 8-jointed, accessory flagellum l-jointed. Antenna 2, ultimate and penultimate 

 joints of peduncle subequal, flagellum 5 — 7-jointed. Gnathopod 1, 6*^ Joint 

 piriforni, longer but narrower than the oblong 6*^ Joint of gnathopod 2. 

 palm concave, very oblique. Peraeopods 3 and 4 with lower front corner of 

 2*^ Joint strongiy convex and setose; peraeopod 5 as in M. inflatus (p. 399). 

 Uropod 1 (not uropod 2) reaching end of uropod 3. Uropod 3 scarcely 

 ^/^5 as long as body, outer ramus about twice as long as inner, with 4 or 

 5 apical and 2 marginal spines and as many setae, inner with only a long 

 apical seta. Telson broader than long, not cleft to the base, lobes conically 

 divergent, tipped with spinules. Colonr white. L. about 10 mm. 



Lake Baikal. 



6. M. glaber (Dyb.) 1874 Gammarus g., B. Dybowsky in: Horae Soc. ent. Ross., 

 ulO suppl. p. 176 t. 14'l"6 1893 Atylus? g., A. Della Yalle in: F. Fl. Neapel, i>. 20 

 p. 928 I 1899 Micruropus g., T. Stebbing in: Tr. Linn. Soc. London, ser. 2 v.l p.424. 



Peraeon segments 6 and 7 each with 2 long setae on bind margiu, 

 pleon Segments 1 — 4 with long, isolated setae on the whole upper surface, 

 Segments 5 and 6 with groups of delicate spinules. Head, rostrum a slightly 

 depressed, rounded point. Side-plates 1^ — 4 with isolated setae. Eyes of 

 moderate size, rounded reniform, black. Antenna 1 about '/* '^^ long as 

 body, about '/:{ longer than antenna 2, but with peduncle ratlier shorter, 

 flagellum 1 l-jointed. Antenna 2, ultimate and penultimate joints of peduncle 

 equal, flagellum 4-jointed. Gnathopod 1, 6*^ Joint in 6 larger than oblong 

 (i'^'i Joint of gnathopod 2, which it rauch resembles in shape, but that the 

 much more oblique palm adds to its length, the pai't bounded by the bind 

 margiii being in both gnathopods oblong. Peraeopods 3—5, 2'^ Joint with 

 lower front corner little or not at all inflated, but setose; in peraeopod 

 5 this Joint is ti'apezoidal, with numerous and long setae on bind margin. 

 Uropods 1 and 2 reaching last fourth of outer ramus of uropod 3. Uropod 3 

 about ^/g as long as l)ody, outer ramus with apical spines and setae, 1 spine 

 on inner margiu, 2 pairs of spines on outer, inner ramus scarcely '/s 

 as long as outer, with 1 apical seta. Telson cleft to base, lobes conical, 

 with some armatm-e. Colour white. L. 9 mm. 



Lake Baikal. 



Das Tierreich. 21. Ldef.: T. R. ß. Stebbing, Amphipoda I. 26 



