258 OLIGOCHAETA 



better termed 'fan-shaped'; the free end is expanded, and apparently cleft into 

 about seven 'teeth.' These are, however, united by a delicate membrane. As the 

 absolute extremities of the teeth are bent over all in one direction, the shape of the 

 setae is highly suggestive of that of a rake. There is but one species: — 



Heteroehaeta costata, CLAPAnfeDE. 

 H. costata, Clapaejide, Beobacht. wirbeU. Thiere, 1863, p. 35. 



Definition. Length about 15 mm. ; nnmber of segments ahout 40. Ventral setae of anterior 

 segment and dorsal setae of Il-IF have the prongs nearly equal ; in dorsal and ventral setae 

 of posterior segments lower prong shorter than upper ; niimher of setae in a bundle, 4 (/J) 

 to 14 (fill) dor sally ; in ventral bundles, i (XXV) to 5 (F). Hob. — Coasts of England 

 and Belgium; Marine. 



There is a certain amount of variation in the arrangement of the setae. The 

 palmate setae sometimes extend further. There has, however, been no detailed study 

 of these variations. Setae of the pectinate variety occasionally occur, but, apparently, 

 so rarely that their occurrence cannot be regarded as either a generic or a specific 

 character. The species is fully illustrated in Benham's memoir, and a few figures are 

 given by CLAPAEiiDE. 



Genus Peloscolex, Leidy. 



Depiwitioit. Each segment with a circle of prominent tubercles. Dorsal setae 

 entirely capilliform, ventral setae uncinate. 



There is but one species, viz. : — 



Peloscolex variegatus, Leidt. 



p. variegatus, Leidy, P. Acad. Nat. Sci. Philadelphia, 1850, p. 134. 



Definition. Length 4 lines. Six to ten setae in each dorsal bundle. Two to three in ventral 

 bundle. Hab. — N. America. 



It is quite clear that this worm is a Tubificid. The characters of the setae are not 

 of themselves sufficient to prove this ; but the statement that the clitellum occupies the 

 tenth segment, added to the characters of the setae, is not reconcileable with its location 

 in any other known family. Vejdovsky (24, p. 45) includes it among the Tubificidae 



