situated subventrally near distal margin, both short, light brown, one anterior, 

 the othei' posterior; a row of small spinules ventrally. Claw large, longer 

 than tarsus, slightly curved, reddish apically pointed, its basal seta in form 

 of large, yellow spine. 



Mid-coxa (Figure 638, B) moderately long; anterior basodorsal seta 

 long, thin, longer than coxa, accompanied by 2 short setae; anterior apical 

 dorsal seta also long; 2 thin setae further distally; posterior apical dorsal 

 seta situated near apex of depression, strong, moderately long; 2 similar 

 setae further distally near margin; 3 large, thin, secondary setae dorsally; 

 anterior primary setae situated in middle, thin, strong, one subdorsal, 

 moderately long, other subventral, short; distoventral setae short, in contrast 

 to forelegs, strong, posterior seta lighter and smaller. 



Trochanter slightly darker than on forelegs; anterior and posterior seta 

 small, light; basoventral seta moderately long, light brown, thicker than on 

 forelegs; anterior apical and subapical setae in form of thick, light spines, 

 subapical spine larger and thinner; both posterior setae short, spine-shaped, 

 light; several light chaetoids, and a row of small spinules between the distal 

 setae. 



Femur yellowish venti-ally and subventrally, chestnut brown elsewhere, 

 brownish dorsally; apical dorsal seta short, strong, chestnut brown; 

 basodorsal seta thin, lighter, slightly larger; anterior seta dark brown, 

 moderately long, in form of a very large, thick, long spine; posterior seta 

 385 situated in basal part, dark brown, spine- shaped; primary distoventral seta in 

 form of a large, yellow, subapical spine, second ventral seta absent; ventral 

 margin with very thin, snaall, light spinules of equal size, in contrast to 

 Brachycentrus. 



[386) 



Number and arrangement of gills of O. potanini 



Segment 



Dorsal 



Pleural 



Ventral 



2 



1 (0) 

 1 





1(0) 



3 



1 

 1 (0) 



1 





4 



1 (0) 



1 





5 









6 









Tibia with large distoventral process, yellowish ventrally, chestnut brown 

 dorsally; distodorsal seta moderately long, light, directed upward, 2nd dorsal 

 seta situated nearby posteriorly, shorter, brown, curved distally; dorsal seta 

 of subapical pair light, subdorsal seta situated anteriorly, brown, thicker, 

 procumbent; posterior ventral seta situated distally on process; anterior 

 ventral seta situated subventrally at basal miargin; a row of small, pointed, 

 light spinules between setae ventrally; similar but smaller spinules on 



483 



