Ventral setae of mid-femur in form of light, long, sharp spine in the 

 middle and a long brown seta more basally; posterior primary seta the 

 same, situated subventrally near the apical ventral seta. 



Posterior seta of hind trochanter (Figure 169, C) thin, long; posterior 

 apical ventral seta the same, both brown; posterior subapical seta shorter, 

 light, slightly brownish. Posterior primary seta of femur situated 

 subventrally near the apical margin, long, dark brown; both primary 

 ventral setae situated in middle of segment, the basal (posterior) seta light 

 brown, moderately long, about in the middle, the second ventral seta in form 

 of thin, long, sharp, light spine not situated as in Thamaste s, but much 

 more apically. 



Dorsal and lateral processes of abdominal segment 1 large. Ventral 

 abdominal elliptical areas present on segments 2—7. Lateral line from 

 segment 2 to beginning of segment 8. 



Gills on segments 2-^, presegmental and postsegmental dorsally, the 

 former shorter and thinner than the latter, postsegmental only ventrally; 

 gills of segment 4 smaller than on the anterior segments, sometimes absent 

 on one side. 



Sclerite of segment 9 light, whitish, sometimes with pale brownish 

 margin, large; anterior margin with 3—4 large grayish dots laterally; 

 covering chaetoids in the naiddle only, small, scale- shaped, pectinate 

 apically, with minute spinules; some spinules larger than the others. 

 Setae numerous, long primary anterior-angle and miedioanal setae situated 

 near the posterior margin, most of the secondary setae also long; 3 thick, 

 long setae and 2 thin, much smaller setae between the medioanal setae; 

 6—7 setae between the anterior-angle and the medioanal seta, including 

 setae situated more laterally in the angle; surface subapically with 2 setae 

 on each side, one short, yellowish, the other brown, moderately long. 



Sclerite "b" of anal legs light brown dorsally, its apical margin with a 

 reddish brown stripe laterally and ventrally; chaetoids scale- shaped, combs 

 of spinules, as on segment 9; median apical dorsal seta blackish brown, long, 

 neighboring seta much shorter, contrary to usual, lateral seta thinner, 

 moderately long, subapical seta on the inner margin brown, short, thin, ventral 

 seta brown, thick, moderately long. Sclerite "c" yellowish brown, spinulose; 

 seta small, brown, some distance from the basal angle. 



Claw dark brown, including basal part; setae as in B.bellicosa. 



Case (Figure 170) 14— 18 mm, rarely 20 mm long, made of medium-sized 

 and coarse sand grains, with rough surface, curved, tapering posteriorly; 

 dorsal surface strongly convex, with sand grains of different size; ventral 

 surface slightly flattened but rough, with coarse sand grains; sides of 

 case with larger sand grains, especially posteriorly; posterior end covered 

 by membrane with a large round or elliptical hole. 



Mode of life and habitats. Shore of Lake Baikal, on stones, 

 usually at a depth of 2—5 m. 



Distribution. USSR: Lake Baikal. Not known outside USSR. 



3. Baicalina thamastoides Martynov 



Bebutova, 1941:94—96, Figures 32^49.— Lepneva, 1964:669—676. 



Full-grown larva. Length 10— 12 mm. Head (Figure 171, A) darker 

 than B. bellicosa; sclerites light brownish, spinules dark brown, dots 



127 



