DESCRIPTIONS OF GENERA AND SPECIES 459 



occurs in three or four species of the Ocnerodrilus. Microdrilus shows further 

 resemblances to JBenhamia in having two gizzards in immediately consecutive 

 segments, and three pair of calciferous glands which seem to occupy the very same 

 segments as in Benhamia; so also do those of Millsonia, the penial setae are 

 practically indistinguishable from those of B. crassa; indeed, M. saliens only differs 

 from that species of Benhamia, in the fact, that there is but a single pair of 

 speiTniducal glands, and that the sperm-duct, though it opens independently of the 

 gland, is close to it on the same segment instead of being a segment in front; a 

 difference of perhaps some importance is the fact that in Microdrilus the calciferous 

 glands are arranged as they are in Lumbricus, i. e. they do not all communicate 

 directly with the gut. As one undoubted Acanthodrilus (A. monocystis) has only 

 a single paii- of spei-miducal glands, the line of demarcation between the Acantho- 

 drilidae and the Cryptodrilidae becomes a very thin Hne. 



Genus Microscolex, Eosa. 



Syn. Deltania, Eisen. 



Cryptodrilus, Michaelsbn (in part.). 

 Rhododrilus, Beddaed. 



Dbpinitioit. Setae strictly paired or distant; prostomium complete or incom- 

 plete; clitellum XIII (XIV)-XVI (XVIl). Nephridia paired commencing in 

 II- V. Gizzard present or absent; no calciferous glands. Spermatheoae nearly 

 always present, and, if so, with diverticulum. Spermiducal glands tubular 

 with penial setae; male pores (on XVII, rarely XVIIl) often separate from 

 spermiducal gland pores. 

 This genus was founded by Rosa (17), who described a single species from Italy 

 under the name of M. modestus. Later, the same author added Fletcheb's ' Eudrilus 

 dubius' to the genus, having met with that species and with M. modestus in the 

 Argentine. A third species of the genus, as I define it in the present work, is a worm 

 which I (37) originally referred to a distinct genus Rhododrilus. That genus was 

 defined as foUows :—' Setae in eight rows. Clitellum occupying segments xiv-xvii; 

 atria tubular ; penial setae present ; vasa deferentia opening on to the exterior in the 

 same segment (xvii), but independently of atria ; gizzard present.' 



The foundation of this new genus was, I think, justifiable at the time. But it 

 cannot be any longer retained. The principal point of difference from Microscolex 

 was (supposed to be) the separate orifices of the sperm-ducts and the spermiducal 



3Na 



