/oqQ\ Number and arrangement of gills 

 of O. m a c u 1 a t u m 



Mandibles (Figure 642, B, C) short, massive, dark brown; teeth situated 

 distally; on left mandible, subventral tooth projecting, larger than others, 

 between 2 similar large teeth, 2 small, i-ound, tooth-shaped processes dorsal 



to mai'gin; 4 teeth on right mandible, subventi-al 

 tooth larger than othei'S, 2 dorsal teeth smaller 

 than ventral tooth; brush with relatively large, 

 grayish chaetoids; lateral setae short, strong, 

 dorsal larger than ventral. 



Sclerites of cardo black, with a thin seta. 

 Sclerites of submentum in form of transverse, 

 widely separated plates, with moderately long 

 setae laterally at anterior margin. 



Pronotum with cui'ved, transverse, dark 

 ridge; anterior margin narrow, widei' in middle, 

 reddish brown; lateral margin narrow, brownish; 

 posterior mai^gin wide, separated by a dark 

 reddish brown stripe, with a wide dark reddish 

 brown ridge; ridge and stripe fused near suture 

 into a wide, dark reddish brown, median, 

 posterior margin; brown part of margin with 

 large light spots; chaetotaxy as in Oligo- 

 plectrodes, with minor differences . 



Mesonotum (Figure 643) incompletely sclerotized with membranous 

 posterior and lateral parts; a straight suture divides each half in 2 parts, 

 median and lateral, both oblong, as in Oligoplectrodes; median sclerite 

 with light dots posteriorly; lateral sclerite slightly wider anteriorly, 

 without oblique streaks or seta posterioi-ly; median sclerite posteriorly 

 with a row of 3 setae instead of 11 large setae, 2 of the 3 setae large, brown; 

 3rd short, yellowish; a small seta closer to lateral margin. 



Metanotum without curved transverse groove; 2 pairs of sclerites: 

 posterior median and lateral; anterior median sclerites absent; median 

 sclei'ite with 4—5 large brown setae, lateral sclerite with 6 strong, 

 moderately long setae and 5—7 thin setae of different size. 



Segment 



Dorsal 



2 



4-6 



3 



4-7 



4 



3-5 



5 



3-5 



6 



2-3 



7 



2-3 



390. 



Number of setae in natatorial combs ofO. maculatum (after Nielsen) 





Tibia 



Tarsus 





segment 1 



segment 2 



segment 3 



segment 4 



( dorsal 



Foreleg < 



° \ ventral 



wjT ( dorsal 



^''"''^ (ventral 



14-15 

 9-16 



53-71 

 43-53 



7-13 

 7-11 



52-68 



47 



8 

 2 



26-27 

 18-23 



3 



16-19 

 9-12 



2-3 



9-12 

 6-7 



Legs mainly yellowish brown, similar to those of O. pot an in i in size, 

 form, and chaetotaxy; ratio of length of legs 48:100:102. 



Fore coxa (Figure 644, A) dark, blackish on dorsal side at base and at 

 margin; tibia wider distally; tarsus shorter than tibia; claw much longer 

 than tarsus; chaetotaxy as in Figures 644, A and 645, A. 



488 



