1892.] SPECIES OF EARTHWORMS. 667 



I. Family Acanthodrilid^. 



The majority of the new species of Acanthodrihdse which I describe 

 in the present paper are from New Zealand ; I owe these specimens 

 to the great kindness of Prof. T. J. Parker, F.R.S., and of Mr. W. 

 W. Smith, of Ashburton. 



The species of Acanthodrilidse found in New Zealand have been 

 hitherto referred to three genera ; six years ago I described, under 

 the name of Neodrilus monocystis^, an Acanthodrilid differing from 

 the typical forma (included within the genus Acanthodrilus) by the 

 presence of but a single pair of atria and spermatothecse ; this worm 

 has been lately re-investigated by Dr. Benham^ 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 abnor- 

 mality of such a species as Acanthodrilus 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 

 distinctness of Beinodrilus and the recently described Plagiochceta^ . 

 This latter may conceivably be identical with Hutton's Megascolex 

 sylvestris* ; at any rate that species is stated and figured by Hutton 

 to possess numerous setae arranged in couples, which is the principal 

 external character of Benham's Playiochceta. 



The remaining Acanthodrilidse have been all referred by me° to 

 the genus Acanthodrilus. This genus comprises altogether some 

 40 species, of which 8 are inhabitants of New Zealand. Forty species 

 are not, perhaps, an unwieldy number for a single genus : it has never- 

 theless been divided into two genera, Acanthodrilus and Benhamia, 

 by Michaelsen ; Benhamia, it should be remarked, includes Benham's 

 Triqaster. In distinguishing the two genera Michaelsen has not 

 considered the characters of the New Zealand Acanthodrilidse. 

 Benhamia is the name applied to those Acanthodrilidse 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 originally 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 reconsider the 

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



1 " Observations on the Structural Characters of certain new or little-known 

 Earthworms," Proc. Eoy. See. Edinb. 1887, p. 157. 



^ " Notes on two Acanthodrilid Earthworms from New Zealand," Q. J. M. S. 

 vol. xxxiii. p. 289. 



^ Benham, foe. cit. p. 294. 



* " On the New Zealand Earthworms in the Otago Museum," Tr. New Zeal. 

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



' " On the Specific Characters &c. of New Zealand Earthworms," P. Z. S. 

 1885, p. 810. " On the Oligochajtous Fauna of New Zealand," P. Z. S. 1889, 

 p. 377. " On the Structure of three new Species of Earthworms &c.," Q. J. M. S. 

 vol. xxix. p. 102. 



