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Show 1892.] SPECIES O F E A R T H W O R M S . 667 I. Family ACANTHODRIEID^E. The majority of the new species of Acanthodrilidse which I describe in the present paper are from N e w 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 Aeanthodrilidse found in N e w Zealand have been hitherto referred to three genera; six years ago I described, under the name of Neodrilus monocystis1, an Acanthodrilid differing from the typical forms (included within the genus Acanthodrilus) by the presence of but a single pair of atria and spermatothecae ; this worm has been lately re-investigated by Dr. Benham2, who has confirmed and extended m y 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 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 Deinodrilus and the recently described Playiochceta3. This latter may conceivably be identical with Hutton's Megascolex sylvestris4,; 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 Aeanthodrilidse have been all referred by m e 5 to the genus Acanthodrilus. This genus comprises altogether some 40 species, of which 8 are inhabitants of N e w Zealand. Forty species are not, perhaps, an unwieldy number for a single genus : it has nevertheless been divided into two genera, Acanthodrilus and Benhamia, by Michaelsen ; Benhamia, it should be remarked, includes Benham's Trigaster. In distinguishing the two genera Michaelsen has not considered the characters of the N e w Zealand Acanthodrilidae. Benhamia is the name applied to those Acanthodrilidae 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. Soc. Edinb. 1887, p. 157. 2 " Notes on two Acanthodrilid Earthworms from New Zealand," Q. J. M. S. vol. xxxiii. p. 289. 3 Benham, loc. cit. p. 294. 4 " On the New Zealand Earthworms in the Otago Museum," Tr. New Zeal. Inst. vol. ix. p. 352, pi. xv. fig. E. 5 " O n 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. " O n the Structure of three new Species of Earthworms &c," Q. J. M . S. vol. xxix. p. 102. |