550 



OLIGOCHAETA 



The penial setae are a pair to each orifice, but much closer together than 

 the ordinary setae ; they are also much more slender, but not very long ; they are 

 not to be seen with a lens when the worm is dissected. 



There are two pairs of papillae, one in front of the anterior and one behind the 

 posterior, pores, on the border line of segments xvii/xviii, xx/xxi respectively. 



I believe Geodrilus singularis to be merely a variety of this species. It is much 

 smaller (65 mm.), but otherwise agrees very closely. 



Genus OCTOCHAETUS, BEDDABD. 

 Syn. Acanthodrilus, BEDDAKD (in part.). 



DEFINITION. Setae eight per segment, distant ; present on XVIII. Prostomium 

 not dividing buccal segment. Male pores on very prominent papillae. Gizzard 

 in V or VI, or V and VI. Calciferous glands as dilatations of oesophagus; one 

 or two in XV, XVI or XVII, XVIII. Nephridia diffuse ; a peptonephridium 

 present. Dorsal vessel completely double. 



This genus contains but four species, which are all natives of New Zealand, and 

 the above definition of it is somewhat shortened from the original definition given by 

 myself (57, p. 668). On account of the characters of 0. antarcticus the genus cannot 

 be quite so clearly defined as it might otherwise be. This species and 0. multiporus 

 are the only ones which possess penial setae ; but the penial setae are much less 

 specialized in character than they are in other Acanthodrilidae. The three remaining 

 species are very closely allied to each other ; two of them indeed (0. multiporus and 

 0. thomasi) are so near that they can practically be only distinguished by size. 

 I believe, however, that a constant difference in size is a valid specific character, and 

 I have allowed it in the case of the two species Acanthodrilus dissimilis and A. 

 parkeri. 0. huttoni, on the other hand, cannot possibly be confounded with any 

 of the other species of its genus. The principal characters of the three species 

 (leaving out 0. thomasi, which hardly differs from 0. multiporus except in size) are 

 as follows : 



