DESCRIPTIONS OF GENERA AND SPECIES 525 



the definition, as it stands above, is really only applicable to the species Trigaster lankesteri ; for 

 Benhamia rosea HAS penial setae, and a much less extensive clitellum. 



In a paper published subsequently to the one referred to above, MICHAELSEN alters his 

 definition of the genus Benhamia so as to include some of the Acanthodrilidae previously described 

 by HORST ; the following species are the ones which are removed from Acanthodrilidae, and 

 transferred to Benhamia : B. scMegelii, B. buttikoferi, B. beddardi, and also ROSA'S species, B. scioana. 

 The character of more than one gizzard present is thus dropped. 



Later still (13), BENHAM again called attention to the generic subdivisions of the Acanthodrilidae, 

 and proposed to retain both Trigaster and Benhamia, as well as, of course, Acanthodrilus itself. 



The three genera are defined by the use of the following characters : 



1. Acanthodrilus. Gizzard single; calciferous glands present. Anterior nephridia form a compact 

 mass, opening into the alimentary tract. Spermathecae, two pairs in vii and viii. 



2. Trigaster. Three gizzards; no calciferous glands. Clitellum, xiii-xl. Spermathecae in viii 

 and ix, without appendices, and opening posteriorly ; no penial setae ; no dorsal pores. 



3. Benhamia. Clitellum, at most five segments ; two gizzards ; calciferous glands present ; 

 Spermathecae in viii, ix, with appendices; penial setae present; dorsal pores present. 



These definitions may be, perhaps, admitted to distinguish Trigaster and Benhamia ; but Acantho- 

 iln'lus is not correctly defined ; the Spermathecae of that genus lie in viii and ix, and have diverticula ; 

 the anterior nephridia do not always form ' peptonephridia.' Other characters, such as the paired 

 nephridia, are omitted '. 



I shall now venture to give my own views with respect to the generic subdivisions 

 of the family. Neither BENHAM nor MICHAELSEN in distinguishing their genera 

 Trigaster and Benhamia have taken into consideration my species Acanthodrilus 

 multiporus 2 . This worm (see below) has diffuse nephridia, one gizzard, dorsal pores, 

 and no ventral gutter surrounding the male openings. 



It doubtless comes nearest to Benhamia. This species differs from Trigaster and 

 Benhamia in not possessing a marked median pair of folds surrounding the male pores. 



If we include all the species with multiple nephridia into one genus as was 

 originally proposed to be done by MICHAELSEN, this difficulty will be got over ; the 

 name of this genus will evidently have to be Trigaster. I am disposed, however, to 

 divide those Acanthodrilidae with multiple nephridia into three genera; this will 

 permit of the use of more than one character as a generic definition, and is, 

 moreover, in harmony with the geographical range of the species concerned. 



The genus Benhamia nearly restricted to the tropical parts'' 1 of the African 

 continent will be defined thus : 



(i) Setae strictly paired, ventral pairs absent on segment xviii. 



1 BENHAM, however, is of opinion that in Arantlinlriliis a network exists in addition to the paired 

 iii'pliridiii ; this is not the case with the speck's I have examined. 



2 Sec MICHAELSEN'S latest remarks (16), which I have not incorporated in the above. 



s Benhamia bolavi, found in Germany, is doutbless, as MICHAELSEN thinks, an importation. So perhaps 

 are other extra-African species. 



