DESCRIPTIONS OF GENERA AND SPECIES 261 



others among the littoral Tubificidae, which have been but little studied, wiU be 

 found to belong to the same genus. There are no points of special interest in the 

 anatomy of this genus. It comes nearest perhaps to Tuhifex, from which it differs 

 principally in the dilated extremity of the spermiducal gland, and in the chitinous 

 penis. EiSEN placed the gfenus nearer to Psammioryctes, but Stolc's recent investi- 

 gations upon this worm (3) have increased the differences between the two genera, 

 which, however, agree in the division of the spermiducal gland into two chambers, 

 and in the fact that there are glands appended to the spermathecae. It is very 

 possible that both Ilyodrilus perrieri and Ilyodrilus fragilis should also be referred 

 to the present genus. Vaillant (p. 395) has already made the suggestion with 

 regard to Ilyodrilus fragilis. 



I have, however, pointed out (70, p- 487) that capilliform setae are sometimes 

 present, and sometimes absent in worms belonging to a species, which must, I think, 

 be CLAPABiiDE's G. ater, and d'Udekem's Tuhifex benedii. Thus the principal difficulty 

 in the way of regarding these two worms as the same species is removed. Peloryctes 

 inquUina of Zengeb is placed by Vaillant among the synonyms of C. arenarius, 

 but also, evidently by an oversight, mentioned (on p. 435) as a distinct species of 

 CUtellio. It cannot, I think, be distinguished from Clapabede's G. ater. Zengeb 

 attempts to distinguish it mainly by the number of setae in the bundles (an 

 eminently untrustworthy character except when applied with great caution) by the 

 distribution of the papillae, and the presence of more than one pair of hearts. 



(i) Hemitubifex insignis, Eisen. 

 H. insignis, G. EiSEN, Bih. K. Svensk. Akad., 1879, No. 16, p. 13. 

 Definition. Length 25 mm. ; no integumental papillae. Spermathecae with glands at neck. 

 Rah. — Sweden. 

 For a fuller account of the anatomy of this species with illustrations, see Eisen (12)- 



(2) Hemitubifex benedii (d'Udekem). 



Tubifex benedii, d'Udekem, BuU. Acad. Roy. Belg. t. xxii., 2nd pt., 1855, p. 544. 

 Clitellio ater, Clapae^de, M^m. Soc. Phys. Gen. 1862, p. 253. 

 T. papillosus, ClaparJide, Beobacht. wirbell. Thiere, 1863, p. 25. 

 Hemitubifex ater, Beddaed, P. Z. S. 1888, p. 485. 

 Clitellio (Clitellio) benedii, Vaillant, Annel^s, p. 418. 

 ? M"ais pustulosa, Williams, Phil. Trans., 1858, p. 96. 

 Peloryctes inquilina, Zengeb, Bull. Soc. Nat. Mosc, 1870, p. 221. 



