1904.] MAEIXE FAUXA OF ZANZIBAR. 327 



in the character of its jaws, whose structure approximates to those 

 of Eunice siciliensis. 



NiciDiON GRACILIS, sp. n. (Plate XXII. figs. 10. 11.) 



Body slender^ divided into tioo parts, lohich differ in the pro- 

 2^ortions of their segments and the characters of the feet they hear. 

 Frpstomium broad, slightly notched in front ; tentacles short, the 

 middle one 2>rojeGting very little beyond the anterior border of the 

 p'ostomiii/m. Eyes large, half moon shaped. Jaws of the usual 

 form, great dental p)lates with about six teeth each. 



Setce of the usual type. 



Allied to Is. hrevis Ehl?' , but differs in slenderness of bodtj. 

 shortness of tentacles, and other characters. 



Three specimens, of which the two largest want the, hind end, 

 were dredged in Wasin Harbour. :■ 



The body is very slender in proportion to its length, the longest 

 fragment measuring 15 mm. by 1*5 mm., and consisting of sixty-five 

 segments. The single complete specimen is unfortunately undei'- 

 going regeneration of the hind end, and so is useless as a comparison. 

 All three are of approximately the same breadth. 



In life the anterior half of the body is coloured red-brown by 

 dots of colour on a whitish or pink ground, the posterior part 

 being nearly coloiu'less but for the black gut. In one specimen 

 two white collars were formed by the peristomium and setigerous 

 segments three and four, and a white spot occui-red in the middle 

 of each segment just behind the intei-segmental groove. In spiiit 

 the specimens are a uniform dull light bi'own, but one is dai'ker 

 and redder anteriorly. 



Two of the specimens were infested with a parasitic Syllid, the 

 fii'st by one, the second by seven examples ; this species Avas found 

 also on a Nemertine and a Polynoid, and will be described in due 

 course. The head of the tSyllid is buried in the space between 

 two adjacent parapodia. 



The head is nearly as broad as the rest of the body, the bi'oadest 

 part of which is about 4 mm. behind it. Both rings of the 

 buccal segment are fairly long, the second being about half as 

 long as the first. These and the next four or five segments are 

 nearly cylindrical in section, but the next twenty- five t are 

 flattened dorsally and especially ventrally, and become very short. 

 These thirty anterior segments form a contrast to the succeeding, 

 both in their own proportions and in the feet they bear (see text- 

 fig. 66, p. 329). The remaining segments are highly arched 

 dorsally, though the venti-al flattening extends to the anus, aiid 

 a,re from two to three times as long as those of the anterioi- 

 region. The broadest part of the body is about the middle of the 



* 'Florida Aimeliden.' Results of dredging by U.S. Pish Coiiiui. SS. ' Blake.' 

 Harvard, 1887. 

 ■f This number is nearlj^ constant in all three examples. 



