638 OLIGOCHAETA 



The nephridia are paired ; the first pair are larger than the following. In R. 

 ecuadoriensis these nephridia open into the buccal cavity, as in Octochaetus m-ulti- 

 poms. The following nephridia are separable (in JR. gulielmi at any rate) into two 

 series ; the anterior series comprising fourteen pairs have a small funnel, a very long 

 muscular duct, and no caecum. The fifteenth and the following nephridium have 

 a larger funnel, a shorter muscular duct and a caecum. 



As regards the reproductive organs the principal point to be noticed is that the 

 sperauathecae lie in front of the other organs of reproduction and that they are paired 

 pouches of some size. 



This genus is exclusively neotropical in its range ; it has been brought only from 

 the more northerly regions of the South American continent. 



VAILLANT (6) has proposed to unite Rhinodrilus with KINBERG'S genus Geogenia; I do not think 

 that this identification is possible ; the principal reason which led VAILLANT to this conclusion is the 

 fact that in both the genera there are specialized setae near to the male pores. This is, of course, 

 a common character with the Geoscolicidae, and is by no means enough upon which to base an 

 affinity so close as VAILLANT suggests between the New-World and the Old-World species described by 

 KINBERG and PERKIER respectively. Moreover, as VAILLANT does not forget to point out, Geogenia 

 has alternate setae in the anterior segments of the body. 



I myself have suggested (28) the desirability of uniting Rhinodrilus with Anteus. I am not now 

 so convinced that this step, supported also by MICHAELSEN (1O), is quite permissible ; it is true that 

 the differences between species referred to Rhinodrilus and species referred to Anteus are not very 

 great ; but, as a matter of fact, it is not an easy task to distinguish Geoscolex from Anteus, and Antrim 

 from Tykonus ; all these South American genera seem to fade into one another; that is to say, the 

 extreme types of each are only to be separated by small differences. If we compare Rhinodrilus and 

 Anteus, it appears that there are hardly any points which distinguish them ; while we had only 

 PERRIER'S (3) description of Anteus with which to compare Rhinodrilus, it was an easy matter 

 to separate the two ; but the description of A. heterostichon by myself (28), and the additional facts 

 in the structure of A. gigns given by HORST (6), bring the two closer together. The chief distinguishing 

 mark is undoubtedly the long retractile prostomium of Rhinodrilus. 



MICHAELSEN (1O), who proposes to unite not only Anteus and Rhinodrilus, but also Urobenus, 

 remarks that the prostomium varies, even in individuals ; but he gives no details as to the exact 

 form of the prostomium in the species of which he treats; with regard to 'Anteus' brunnens, however, 

 he speaks of it as retracted, ' mehr oder weniger weit eingezogen.' This suggests a Rhinodrilus-like 

 prostomium ; and, as a matter of fact, this species appears to me, on other grounds, to be referable to 

 the genus Rhinodrilus. 



I referred in the paper already quoted to the apparently greater number of calciferous glands in 

 Rhinodrilus; this difference no longer holds, for R. brinnieus (MICHAELSEN) has, like Anteus, three 

 pairs only. 



PERRIEE (3, p. 65) does not consider that the characters drawn from the cephalic lobe are sufficient 

 to separate genera alone ; but I think it possible from the remark, ' cette trompe n'a du reste aucun 

 rapport avec Fappareil digestif,' that PERRIER did not thoroughly investigate the structure of the 

 peculiar prostomium of Rhinodrilun, or he would possibly have given more weight to its value as 

 a diagnostic character. 



