23 (22) Genital setae (penial, or spermathecal, or both) present 24 



23 (22) Genital setae absent 29 



24 (23) Somatic setae broad, bifid, with upper tooth shorter and much thin- 

 ner than lower (Fig. 41). Spermathecal setae three to four per 

 bundle, single-pointed to very faintly bifid (Fig. 42). External male 

 pore single, median Smithsonidrilus marinus 



Figure 41 (left). — Somatic seta. 

 Figure 42 (right). — Spermathecal seta. 



24 (23) Somatic setae not of previous form. If present, spermathecal setae not of previous 



form. External male pores paired, ventrolateral 25 



r 



25 {2A) Posterior dorsal setae one per bundle with strongly curved ends 

 and small thin upper teeth (Fig. 43). Posterior ventral setae 

 normal bifids, much smaller than dorsals (Fig. 44). Sperma- 



tozeugmata present. Spermathecal setae present 



Isochaeta hamata 



Figure 43 (left). — Dorsal seta. 

 Figure 44 (right). — Ventral seta. 



25 (2A) Posterior dorsal setae more than one per bundle and not of previous form. Sperma- 



tozeugmata absent. Spermathecal setae absent 26 







26 (25) Posterior dorsal setae single-pointed, strongly curved (Fig. 45). 

 Penial setae of two types; each penial bundle contains one giant pe- 

 nial and 8 to 12 small clubbed penials with small reflexed distal tooth 

 (Fig. 46). Two prostate glands join each pear-shaped penial bulb 

 (Fig. 47) Adelodrilus anisosetosus 



Figure 45 (top left). — Dorsal seta. 



Figure 46 (top right). — Distal end of small 



penial seta. 

 Figure 47 (bottom). — Lateral view of male 



genitalia; A, atrium; B, penial bulb; G, 



giant penial setae; P, prostate gland. 



26 (25) Posterior dorsal setae not as Figure 45. Penial setae of one type; penials approximately 



the same size as the somatic setae. Two prostate glands attached to each atrium 27 



12 



