short, relatively thin; seta 15 moderately long, thin; seta 16 light, procum- 

 bent; seta 17 slightly larger than 7. Ventral seta 8 small, thin; seta 18 small. 



Labrum (Figure 447) with deep anterior median depression; dorsal 

 sclerite brown, with a brown spot behind median pit; posterior- angle 

 sclerites dark, curved at a right angle. Setae as in Figure 447; seta 1 in 

 form of short, thick, blunt spine thicker in middle, situated slightl}' ventrally. 



(257; 



FIGURES 447— 451. Potamophylax n i gr i c or n i s Pict. (after Nielsen): 



447— labrum; 448 — left mandible, dorsal (A), lateral (B), and ventral (C); 

 449 — maxillolabium; 450 — part of pronotum, propleuron, and base of fore 

 co,\a, lateral; 451 — mesonotum, metanotum, mesopleuron, and metapleuron. 



Mandibles (Figure 448) black, short, with a distinct groove between distal 

 and basal part; teeth blunt; dorsal blade of left mandible with 2 teeth in 



322 



