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. 

 Fi^re 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 



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



tozeugmata absent. Si^ermathecal 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) Adelodrihis 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 



