CH^ETOZONE SETOSA. 265 



1909. Chvetozone setosa, Percy Moore. Proc. U. S. Nat. Mus., vol. xxxvii, p. 139. 



1911. „ „ Mcintosh. Ann. Nat. Hist., ser. 8, vol. vii, pp. 165, 166, 169, and 170. 



1913. „ ,, Augener. Zool. Anzeiger, Bd. xli, p. 261. 



1914. „ „ Southern. Proc. Roy. Irish Acad., vol. xxxi, no. 47, p. 119. 



Habitat— Station 7 (1890) S.W. Ireland (R.I.A.) ; Clare Island district (Southern). 



Abroad it is noted from Greenland (Michaelsen) ; Spitzbergen, Norway, Sweden, and 

 Finmark (Malmgren) ; Spitzbergen (Fauvel). Abundant in the Fjords of Norway, such 

 as Lervig Bay, off Drobak, etc. (coll. A. M. Norman) ; 300 fathoms, off Norway (Sars) ; 

 Atlantic coast, U.S.A. (Verrill) ; Siberian and Behring seas (Wiren) ; Kara-Havets, etc. 

 (Levinsen) ; Franz- Joseph Land (Augener), 



Head acutely pointed and somewhat triangular, with the mouth on the ventral surface 

 (of the peristomium) a short distance from the tip. 



Body about an inch in length, elongate-fusiform, tapering a little anteriorly and 

 more gradually and distinctly posteriorly, where it terminates in a pointed extremity with 

 the anus at the tip, which varies in acuteness according to the condition of regeneration, 

 some being rather blunt after recent loss of segments. The thickest part of the body is 

 about the end of the anterior third. It is more or less rounded throughout, with a 

 tendency, however, to dorsal and ventral flattening. The segments number seventy to 

 ninety, and are narrow in front, but more evident posteriorly, where their antero-posterior 

 diameter is greater. The surface is greyish in the preparations and is iridescent. The 

 long tentacles arise on the dorso-lateral region immediately behind the head, and seem to 

 be rarely present in dredged examples. They have the ventral and probably ciliated 

 groove of other forms. The branchiae occur in pairs, one on each side, probably from 

 fourteen to twenty in succession, and then at intervals to the posterior third. They are 

 slender filaments, those in front being long and sinuous. 



The first bristled foot occurs behind the tentacles, and has a dorsal and a ventral 

 tuft of pale golden capillary bristles with a more or less cylindrical shaft generally 

 inserted in the tissues, and a broader, flattened, serrated tip, which tapers to a fine point. 

 In the anterior region little difference exists between the length of the dorsal and the 

 ventral bristles, both of which are directed backward, but after the twentieth or thereabout 

 the dorsal become more elongate, forming glistening tufts, usually borne transversely in 

 the preparations, and almost equalling in some the diameter of the body. 



Toward the posterior region stout, short, crotchet-like forms appear in the ventral and 

 then in the dorsal amongst the longer bristles. They are more slender in the dorsal than in 

 the ventral, and the dorsal bristles are fewer in number and proportionally more attenuate, 

 only a brief flattened part occurring beyond the skin, the rest being hair-like. Moreover, 

 the ventral bristles present intermediate forms, the shafts being about three times the 

 diameter of the ordinary bristles, then a slight constriction occurs at the level of the cuticle, 

 the tip being broad and more or less striated, but terminating in a long hair-like process. 



The perfect organ (crotchet-like or acicular bristle) is best seen in the posterior region, 

 comprising about fifteen segments, where it is in full strength (Plate CV1I, fig. 4). The 

 shaft dilates a little from the soft base upward, then narrows slightly about the level of 

 the skin, from which a noticeable anterior bend occurs, the long, stout tip ending in a blunt 

 point. The whole organ is striated almost to the point and somewhat resembles a 



157 



