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long; 6 secondary posterior distodorsal setae in addition to long, thick, 

 primary seta. Anterior seta of trochanter short, light; brown posterior 

 seta longer than setae of the coxa; posterior apical ventral seta long; 

 apical seta light, moderately long; both anterior ventral setae in form 

 of light, sharp, widely spaced spines; basoventral seta grayish, thick, 

 long, like the apical ventral seta. Basodorsal seta of femur only slightly 

 longer than apical dorsal seta; short, thin anterior primary seta situated 

 distally; posterior seta brown, long, larger than the dorsal setae, situated 

 ventrally; one almost equally long, basoventral, secondary seta; primary 

 ventral setae situated in middle of segment, apical one short, thick, 

 spine- shaped, the basal one situated nearby, in form of a large, sharp, light 

 spine. The subdorsal of the 2 long primary, distodorsal setae of the tibia, 

 contrary to the usual, dark brown, longer than brown dorsal seta; 2 

 secondary dorsal setae also large, longer than posterior seta of the femur; 

 2 long, brown dorsal secondary setae in middle of tarsus. 



Lateral line on segments 2—7. Gills on segments 2—6; dorsal preseg- 

 mental gills of segments 2—3 small, thin; postsegmental gills of these 

 segments with thick, long filaments; ventral postsegmental gills of 

 segments 2—3 smaller than dorsal gills, those of segments 4—5 small, 

 and on segment 5 also thin. 



Tergite of segment 9 grayish, with indistinct punctation, without 

 spinules; setae numerous, medioanal setae blackish brown, longer and 

 thicker than anterior -angle setae; the other 25—27 setae, short and 

 moderately long, dark brown and blackish (Figure 201 ). 



Sclerite "b" of anal legs (Figure 202) pale grayish, brown laterally 

 and ventrally at distal margin, with small spinules in rows of 2—4; medio - 

 distal seta larger than others, thick, black, long; neighboring seta dark 

 brown, much shorter, thick; lateral seta thin, brown, moderately long; 

 apical and subapical naedian margin setae similar, the former slightly 

 longer; ventral seta thin, moderately long. Sclerite "c" reddish brown, 

 with broad, blackish brown lateral margin; seta light, thin, relatively large. 



Claw reddish brown distally, with a small dorsal denticle; seta 1 short, 

 light, thick; seta 3 brown, moderately long, situated near base of distal part, 

 both setae subdorsal; seta 6 situated near suture margin, moderately long; 

 seta 2 situated near end of suture, slightly longer; both setae thin, brown; 

 ventral setae 7 and 8 light, thick; setae 5 and 4 small, situated basally, 

 the former lateral, the latter medial. 



Case 7—8 mm long, made of small sand grains, slightly curved, narrower 

 posteriorly; dorsal surface convex, ventral surface flattened; separate 

 large sand grains at sides of ventral margin. 



Mode of life and habitats. Running water : cool rivers and 

 rivulets, close to the surface, at a depth of less than 1 m, in parts with 

 slow current; in springs with a summer temperature not over 12—13°; 

 on stony bottom among vegetation; feeding on diatoms. 



Distribution. Northeastern part of the European USSR (Bol'she- 

 zemel'skaya Tundra, Northern Urals), Western Siberia (Kara Tundra, 

 Tomsk), Altai, Eastern Siberia (Minusinsk and Krasnoyarsk, lower reaches 

 of Yenisei, Lower Tunguska, Kolyma delta, lower reaches of Lena and 

 Yakutsk, Anadyr), Kamchatka, Maritime Territory and Amur Region, 

 Shantar Islands. In addition, Canada. 



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