DESCRIPTIONS OF GENERA AND SPECIES 507 



There is a greater range of variation among the species of this genus than is the 

 case with the related Ocnerodrilus. 



The four species, G. elegans, G. ditheca, G. dominicensis, and G. zanzibaricus, form 

 a distinct group, characterized by their small size, by the absence of a gizzard, and 

 by the fact that the spermathecae do not communicate with the exterior by a long duct. 



G. robustus is a stouter species, though small, with paired calciferous glands, 

 with a well-developed gizzard, and with spermathecae with a long duct. The most 

 abnormal species is, however, G. tenuis, which has some claims to be placed apart 

 in a separate genus. It is extraordinarily long, and the ventral setae, like those of 

 Megachaeta, are very much larger than the dorsal ; the pores of the spermiducal 

 glands are much further back than in the other species, and there is but a single 

 pair of testes. 



G. robustus serves to connect the genus Gordiodrilus with the nearly-related 

 Ocnerodrilus. 



As in Ocnerodrilus the ventral setae, near to which the spermiducal glands open, 

 are present or absent. In G. tenuis these setae are present and unaltered ; in G. elegans 

 they seem to be completely absent ; in G. zanzibaricus one of the two setae of the 

 ventral pair only is absent, the others being present and unaltered. The amount of varia- 

 tion in the position of the male pores is unusual. In G. robustus and G. zanzibaricus 

 the pores of the spermiducal glands are upon segments xvii, xviii ; in G. elegans they 

 have moved a segment further back and are upon xviii, xix ^ G. tenuis is in this, 

 as in other respects, most abnormal ; the pores in question are in that species upon 

 segments xx and xxi. The various pores connected with the male efferent apparatus 

 open on to a pronounced ridge, one on either side, with an undulating outline, being 

 deeper at the two ends than in the middle. The two ridges seem to join in front and 

 behind, forming thus a sucker-like structure. 



(i) Gordiodrilus tenuis, BEDDAED. 

 G. tenuis, BEDDARD, Ann. and Mag. Nat. Hist., July, 1892, p. 75. 



Definition. Length, 90 mm. ; diameter, i mm. Ventral setae, present on genital segments, 



four times the size of lateral setae. Clitelltim, XI7-XXVII, saddle-shaped. Spermiducal 



gland pores on XX, XXI, behind setae ; male pore on XX 7, in front of setae. Septa, 



V/XII, thickened. Testes, one pair in XT; sperm-sacs in X-XIII. Spermathecae, two 



pairs, with long duct. Hab. Assaoa, W. Africa. 



1 In my paper upon this genus there is unfortunately some little confusion as to this matter ; the 

 segments are rightly stated on one page, and misstated on another. 



3 T 2 



