SIBOGLINUM ZANZIBARICUM 315 



half times as long as the diameter of the tube. Seven rings gradually appear 

 in each segment, beginning in the hind part of each one (Fig. UU133^). 

 The ring-length is a fifth to a quarter of the diameter of the tube and the 

 clear interspaces are the same length (Fig. UU1332?). The segmentation 

 soon breaks down and the rings become longer. They are very regular and 

 brown with a lustrous surface (Fig. UU133C). In the middle of the tube 

 clear streaks appear down the centre of each ring, dividing it into two 

 secondary rings of which the anterior is darker than the posterior (Fig. 

 UU133Z)). In the final third of the tube the rings are longer (half the diameter 

 of the tube), but each has a clear central streak of "chinks" and "openings". 

 The substance of the ring, moreover, is not homogeneous, but consists of 

 small dark conspicuously more compact patches or blotches (Fig. UU133£.) 

 This peculiarity increases towards the hind end of the tube (Fig. UU133.F). 

 The hindmost part of the tube is torn off. The length of the tube is 90 mm, 

 its anterior diameter OT35 mm and its posterior 0-09 mm. 



The various features of S. sumatrense are all encountered separately in 

 different representatives of this genus, but the species is sufficiently charac- 

 terized by their combination. The most noticeable specific peculiarities 

 S. sumatrense are the even width of the keels of the bridle and their dorsal 

 and ventral separation, the absence of any glandular girdle behind the 

 bridle, the poor differentiation of the metameric papillae and the nature of 

 the tube. Though the tube of S. sumatrense is very like that of S. ceylonicum 

 sp. nov. (p. 301), it is distinguished from the latter species by the poorly 

 developed anterior group of teeth on the platelets of the girdles. 



Material : one tube with an animal and one empty fragmentary tube. 



Locality: Vitya£ station 4543 (31st cruise): Indian Ocean near the south 

 coast of Sumatra near the entrance to Sunda Strait. 



Substratum: grey muddy sand. 



Depth 626 m.] 



[37. Siboglinum zanzibaricum sp. nov. Ivanov (Figs. W133, WW133) 



One specimen of this rather large species of Siboglinum was found in the 

 contents of a dredge haul taken by R.V. Vitya£ on 17 March, 1960, to the 

 east of the Islands of Zanzibar and Pemba at a depth of 2173 m. 



The fore-part of the body is very short, probably as a result of strong 

 contraction when the fixative was added. It reaches its greatest breadth in 

 the region of the bridle and gradually tapers from there to the tip of the 

 cephalic lobe (Fig. W1332?, C). The length to breadth ratio is 3-5 : 1. The 



