8 (7) Worms up to 25 mm long. Longest seta of segment II more than 200 /^ long, 4.5 /a 



thick. Penial setae three to five per bundle Chaetogaster diaphamis 



8 (7) Worms up to 7 mm long. Longest seta of segment II less than 165 fj. long, 2 /x 



thick. Penial setae two per bundle Chaetogaster cristallmus 



9 (2) Prostomium produced into long proboscis 



(Fig. 10) Stylaria lacnstris 



Figure 10. — Ventral view of anterior segments, 

 showing elongate prostomium. 



9 (2) Prostomium rounded 10 



10 {9) Teeth of needle setae (dorsal crochets) long and nearly parallel 

 (Fig. 11). Upper tooth of all ventral setae about twice as long as 

 the lower (Fig. 12) Nais elinguis 



Figure 11 (left). — Distal end of needle seta. 

 Figure 12 (right). — Ventral seta. 



H 



10 (9) Teeth of needle setae short, diverging (Fig. 13). Potserior ventral 



setae with approximately equal teeth (Fig. 14) 11 



Figure 13 (left).— Needle seta. 



Figure 14 (right). — Ventral seta from a posterior segment. 



M 



; / 



11 (10) Ventral setae of segments II to V with upper tooth longer than lower; setal 



teeth diverge at an angle less than 45° (Fig. 15) Nais variabilis 



Figure 15. — Ventral seta from an anterior segment. 



11 (10) Ventral setae of segments II to V similar to posterior setae, with nearly equal 



teeth; setal teeth diverge at an angle greater than 45° (Fig. 16) 



Nais communis 



Figure 16. — Ventral seta from an anterior segment. 



