164 Transactions. — Zoology. 



cystis/'- an Acantliodrilid differing from the typical forms (in- 

 cluded within the genus Acanthodrilus) by the presence of but 

 a single pair of atria and spermatothecaB. This worm has been 

 lately reinvestigated by Dr. Benham,f who has confirmed and 

 extended my original account. I may add that I have within 

 the last few months received some more examples of the same 

 worm. There is, accordingly, no longer any doubt as to the 

 characters of this species. It is not, as I at first thought it 

 might be, a mere abnormality of such a species as Acantho- 

 drilus dissimilis. "Whether this earthworm should be really 

 referred to a distinct genus is another matter. I prefer, 

 however, to leave the question alone for the present. In any 

 case, there can be no doubt whatever about the generic dis- 

 tinctness of DeinodriUis and the recently-described Plagio- 

 chcBta.l This latter may conceivably be identical with 

 Untton' s Megascolev sylvestris ;^ at any rate, that species i& 

 stated and figured by Hutton to possess numerous set®, 

 arranged in couples, which is the principal external character 

 of Benham's Plagiochata. 



" The remaining AcantliodrilidcB have been all referred by 

 mell to the genus Acanthodrilus. This genus comprises alto- 

 gether some forty species, of which nine are inhabitants of 

 New Zealand. 1i Forty species are not, perhaps, an unwieldy 

 number for a single genus ; it has, nevertheless, been divided 

 into two genera — Acanthodrilus and Benhamia — by Michael- 

 sen. Benhamia, it should be remarked, includes Benham's 

 Trigaster. In distinguishing the two genera, Michaelsen has 

 not considered the characters of the New Zealand Acantho- 

 drilidcB. Benhamia is the name applied to those Acantho- 

 drilidce with a ' diffuse ' nephridial system — that is, in which 

 the nephridia are not paired, but open on to the exterior by 

 numerous pores. Added to this character, Michaelsen origin- 

 ally called attention to the fact that the species with a diffuse 

 nephridial system possess a pair of gizzards, or, as in Trigaster, 

 three gizzards. Later he was led, by a consideration of the 

 species Acanthodrilus schlegelii, to consider the definition of 

 the genus, and to use, as part of the generic diagnosis, the 



* " Observations on the Structural Characters of certain New or 

 Little-known Earthworms," Pro. Roy. Soc. Edin., 1887, p. 157. 



t " Notes on Two Acanthodrilid Earthworms from New Zealand." 

 Q.J.M.S., vol. xxxiii., p. 289. 



+ Benham, loc. cit., p. 294. 



§ " On the New Zealand Earthworms in the Otago Museum," Trans. 

 N.Z.Inst., vol. ix., p. 352, pi. xv., fig. E. 



II " On the Specific Characters, &c., of New Zealand Earthworms." 

 P.Z.S., 1885, p. 810. "On the Oligocluifitous Fauna of New Zealand," 

 P.Z.S., 1889, p. 377. " On the Structure of Three New Species of Earth- 

 worms, &c.," Q.J. M.S., vol. xxix., p. 102. 



11 I have recently sent several specimens to Mr. Bcddard, some of 

 which will, T think, prove to be new species of Acanthodrilus. 



