1892.] SPECIES OF EARTHWORMS. 671 



always present ; no ventral setce upon xviii. — Distribution : Tropical 

 Africa, Tropical America, and India. 



The species Acanthodrilus novce-zelandice, A. dissimilis, A. rosce, 

 and A. smitlii (to be described in the present paper) I refer to the 

 genus Acanthodrilus sensu stricto. I am doubtful about Acan- 

 thodrilus annectens, a species which I described some years since ^. 

 In possessing paired nephridia it agrees with Acanthodrilus (s. s.), 

 but it has the " mucous gland " of Octochcetus, and the gonads are 

 placed in contact with the funnels of their ducts, as is the case with 

 three of the species which I refer to this genus, Octochcetus ; it has 

 the further peculiarity that the sperm-ducts run in the thickness 

 of the body-wall, a peculiarity which it apparently shares with the 

 genus OctoclicBtus, but which, among other Oligochseta, is rare, and 

 only found, so far as I am aware, in Biplocardia communis and 

 in the not nearly allied form Siphonogaster. The absence of cal- 

 eiferous glands is occasionally met with in Acanthodrilus. The 

 existence of this species serves to indicate how closely allied are the 

 forms which do, and the forms which do not, possess a diffuse 

 nephridial system. Another instance of the same approximation of 

 species to each other which differ in their excretory system is afforded 

 by Benhatnia heddardi and Acanthodrilus ungulatus ; in both of 

 these there is an elaborate arrangement of modified setse and glands 

 appended in the neighbourhood of the spermatothecse. These facts 

 possibly indicate that the passage from the diffuse to the paired 

 nephridia may occur more than once in a genus, and of course dis- 

 count the value of the modifications of the nephridial system in 

 classification. 



I shall now describe two apparently new species which I refer 

 to my genus Octochcetus :~ 



L. Octochsetus thomasi, n. sp.^ 



I have received on various occasions during the last few years 

 examples of a small-sized Acanthodrilid from New Zealand, which I 

 have hitherto confounded with 0. multiporus. I regarded these 

 individuals merely as small specimens of that species. A full-sized 

 specimen of O. multiporus is a very large worm, measuring, even 

 in a contracted condition, some 14 inches in length by half an inch 

 or so in breadth. On the other hand, the worms which I now 

 consider to represent a new species of this genus are of a much more 

 slender build. Unfortunately, I am not in a position to give any 

 exact measurements ; the specimens which I possess are none of 

 them intact. An individual measuring 144 mm. is, I fancy, nearly 

 complete; the diameter of this worm is not more than 5 mm., and 

 the body consisted of 230 segments. 



The external characters of the species recall 0. multiporus ; the 

 prostomium is not contiiiued by grooves on to the buccal segment. 

 That segment and the two following are noc annulate ; segments 



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

 vol. xxix. p. 102. 

 * Named after Prof. A. P. Thomas, of Auckland, New Zealand, 



45* 



