DESCRIPTIONS OF GENERA AND SPECIES 291 



This is a small species, not measuring more than 8 mm., or 2 mm. according to 

 LEIDY. VAILLANT has thrown some doubt upon the identity of the American and 

 European forms on account of this difference in size. 



It may also be pointed out that VEJDOVSKY'S figure of this species (24, Taf. ii, fig. 13) indicates 

 no abrupt demarcation between the buccal segment and the comparatively short prostomium ; in 

 the text (24, p. 31) it is remarked 'Der Kopflappen verjungt sich allmalig zu einem konischen, 

 fadenfo'rmigen Russel.' This ' gradual ' narrowing is not shown in LEIDY'S figure, nor in D'UDEKEM'S ; 

 and in a single example (English, but ? exact locality) examined by myself, the prostomium was 

 as illustrated by LEIDY and D'UDEKEM, not VEJDOVSKY. The specimen examined by me being 

 about 4-5 mm. in length connects the two extremes of 2 mm. and 8 mm. As VEJDOVSKY leaves out 

 LEIDY'S Pristina longiseta in the list of synonyms given under the species, and does not mention 

 N. America as a locality for the species, but is acquainted with LEIDY'S paper 1 , I am disposed to 

 infer that VEJDOVSKY is not certain about the identity of his and LEIDY'S varieties. The question 

 must, I think, be left open for the present. 



The prostomium appeared to me to be grooved upon the lower surface, this groove 

 opening into the mouth. The number of segments is 17-20. The dorsal setae are 

 entirely capilliform, two or three are found in each bundle 2 ; those of the third segment 

 are, according to VEJDOVSKY'S figure, about three times the length of those of other 

 segments. The ventral setae are sigmoid and cleft at the extremity ; there are seven 

 or eight to a bundle. The peculiarities of the alimentary canal have been referred to 

 under the genus. The dorsal vessel is connected with the ventral by four pairs of 

 vascular arches in segments iv-vii (VEJDOVSKY, 21, p. 1*3), of which the last pair is 

 stouter than the rest. These vessels are entirely unbranched and arise from the dorsal 

 vessel just behind the dissepiment. The nephridia commence in the tenth segment. 

 The perivisceral corpuscles have black, brown, or green contents. 



VOELTZKOW has recorded from Madagascar a species very like P. longiseta, but no 

 special description is given. 



(2) Pristina equiseta, BOURNE. 

 P. equiseta, BOURNE, Q. J. M. S., vol. xxxii (1891), p. 352. 



Definition. Length, 8mm.; number of segments, 21. Setae of segment III not elongated; 

 prostomium long. Glandular ventricle in segment VIII. One vascular arch. Nephridia 

 commence in IX. Hab. England (/). 



This species was discovered by BOURNE in the ' Victoria regia ' tank, in the Gardens 

 of the Royal Botanical Society, in Regent's Park, London, whence I had myself 



1 It is not only quoted in list of literature, but the species is referred to in the history of the group, 



P- *Z- 



3 Three to six are figured by VEJDOVSKY, three by LEIDY and D'UDEKEM. 



P p 2 



