DESCRIPTIONS OF GENERA AND SPECIES 



517 



B 



c 



multiporus. Finally, we have in A. capensis an intermediate condition,: the setae 

 are closely approximated in the front region of the body and more separated behind. 

 In the genus Octochaetus, as in Acanthodrilus, the ventral setae of the eighteenth 

 segment are present ; the ventral setae of the seventeenth and nineteenth segments 

 are wanting, being replaced 



by the penial setae. 0. ant- ' 



arcticus and 0. multiporus 1 p 



show an interesting inter- 

 mediate condition ; the setae 

 of the eighteenth segment are 

 present, the male pore lying 

 just dorsad of the outermost 

 of the two. On the seven- 

 teenth and nineteenth seg- 

 ments the penial setae occupy 

 the place of the outer of the 

 two setae of each ventral 

 pair, but the inner setae of 

 the ventral pair are present and 

 apparently unmodified. The 

 penial setae are rather short 

 and often, at any rate, less 

 curved than is usually the 

 case with these setae. The 

 setae of these genital segments 

 are in a simple condition 

 which nearly reproduces the 

 state of affairs in such a 

 form as Gordiodrilus. The 

 genus Kerria, which is in 

 some respects the simplest 

 Acanthodrilid, has no penial 

 setae but only the ordinary and unmodified setae of those segments. 0. antarcticus 

 is only just removed from that simple condition, which is possibly characteristic of 

 ROSA'S A. spegazzinii, and is a reason for placing that species in my genus Kerria. 



1 I erroneously stated in my original description of this worm ',8) that penial sotae were 

 absent. 



XVJl 



XVJII 



XIX 



At 



GENITAL SEGMENTS OF A NUMBER OF ACANTHODEILIDS. 



A. Octochaetus antarcticus. B. Acanthodrilus capemis. C. Henhamia. 

 D. Acanthodrilus smithii. E. Acanthodrilus novae-zelandiae. i Male 

 pore. At. Spenniducal gland pores connected by a groove. Penial setae 

 omitted in D and E. 



