SIBOGLINUM VELERONIS 279 



near the middle, making the total length about 30 mm. The body is nearly 

 uniform in width but is widest in the mesosomal region where it measures 

 0-065 mm; the postannular region gradually becomes slenderer and tapers 

 posteriorly. The tentacle is less than half as wide as the body and extends 

 forwards for a length nearly two and a half times that of the mesosomal 

 length. 



"Individual tubes measure 50-65 mm long by 0T3 mm across. Others are 

 longer or narrower, having a length to width ratio of 450 — 720 : 1. Each 

 tube is usually slender cylindrical, pale to dark straw-coloured and crossed by 

 alternating dark brown rings and pale bands (interspaces). The brown rings 

 are typically paired (Fig. El 335), so that both of a pair are nearly twice as 

 long as one pale interspace. An occasional irregularity in this pattern results 

 when the two dark rings are so close together as to appear fused, or are in- 

 complete on one side to form a broader than usual, incomplete, pale inter- 

 space. The greater length of the tube is crossed by these alternating cross 

 bars; only the distal anterior and posterior ends (Fig. E133/i) are pale and 

 usually collapsed. 



"S. veleronis was recovered from a quantitative sample covering a surface 

 area less than half a square metre. The animals contained in the mud, 

 without tubes, weighed about 64 g (moist weight)." The haul included more 

 than 428 specimens of more than 30 species, of which S. veleronis accounted 

 for more than 100 specimens, 22 species of polychaetes for more than 200 

 specimens and various molluscs for most of the rest. 



Material : more than a hundred specimens. 



Locality : off the coast of Southern California, Velero IV station 7049 : the 

 axis of La Jolla canyon near its convergence with the San Diego trench 

 (32°49 / 37"N 117°35'12"W). 



Depth: 976 m. 



Substratum: grey sand and green mud.] 



[30. Siboglinum subligatum sp. nov. Ivanov(Figs. AA133-DD133) 



I took this species, which inhabits a characteristic whitish tube, on 21st 

 December, 1960, in the trawl on board R.V. Vityaz\ in the western part of 

 the Indian Ocean in the area of the Cargados Carajos Islands (north of 

 Mauritius). The material was generally in a good condition, allowing an 

 unusually thorough investigation of the external morphology of the animal, 

 and embryos were found in some of the tubes. 



The mesosoma, as a rule, reaches a breadth of 0-2 mm. The fore-part of the 

 body, sharply delimited from the metasoma, is greatly elongated, being eight 



