528 OLIGOCHAETA 



This is by far the most extensive of the genera of Acanthodrilidae ; it comprises 

 eighteen well-marked species, besides a few others, of which we have not afc present 

 sufficient knowledge, and which, indeed, may not belong to Acanthodrilus (s. s.) at all. 



To the latter category belong Hegesipyle hanno, of Kinbeeg, wliich Pbeeiee has determined (6) 

 to be a.n Acanthodrilus ; Mandane stagnalis, Kinbeeg, no doubt a true Acanthodrihts, since thia is the 

 only genus of the family which occurs in S. America; Lumhricus kerguelarum, Geube, has been 

 shown by Michaelsen (10) to be referred to the Acanthodrilidae, and is perhaps synonymous with 

 Lankestee's a. herguelenensis. Finally, we have several species of 'Lumhricus' described by Hutton 

 (1), which are, no doubt, as Hutton himself pointed out later (3), referable to the genus Acantho- 

 drilus [sensu lata) ; probably most of these species are identical with those subsequently described 

 by myself from New Zealand. 



The identity of Mandane with Acanthodrilus was suspected by Peeeiee (3) and afterwards (6) 

 proved; the name, however, cannot stand, as Kinbeeg used the same name in the same paper for 

 a genus of Polychaeta ' ; neither can Hegesipyle ; for, although Peeeiee has shown it to be an 

 Acanthodrilus, it is not clear whether it is referable to this genus in the strict sense. 



The species of the genus Acanthodrilus vary in si2e from an inch or so to twelve 

 inches and upwards. It is one of the few genera which comprises aquatic as well 

 as terrestrial forms. A. dalei and A. aquarum dulcium (see Beddaed [43]) occur 

 in streams in the Falkland Islands and ' Mandane ' stagnalis was obtained from 

 a pond near Montevideo. A. schmardae occurs in fresh water in Queensland. The 

 prosiomium shows differences which are usually, in other families of Oligochaeta, 

 correlated with a sufficient number of other differential characters to be of generic 

 value. In some species (e. g. A. novae-zelandiae) the prostomium is prolonged 

 backwards so as to completely divide into two the buccal segment ; in others it is 

 not prolonged back so far or is merely a pr^ection, separated from it of course by 

 a groove from the buccal segment. 



The setae again show no such constancy of arrangement as is commonly met with 

 in a single genus. In some species the individual setae of each couple are very close 

 together ; in others they are not. In A. capensis we have the intermediate condition ; 

 the two setae of each couple are closely approximated anteriorly, wider apart 

 posteriorly. In A. falclandicus the lateral setae are further apart than the 

 ventral setae. 



Apart from the paired nephridia and the single gizzard there are no very salient 

 differences between Acanthodrilus and Benhamia. I have noticed, however, that 

 in Benhamia the calciferous glands are very distinct from the oesophagus ; they have 

 the shape of reniform pouches, attached to the sides of the oesophagus. As a rule, 



^ This extraordinary departure from the usual laws of nomenclature was first pointed out by Pekcival 

 Wright. Zoological Record, vol. iil. p. 597, footnote. 



