SIBOGLINUM ZANZIBARICUM 



317 



A 



lying on narrow ridges, fuse both dorsally and ventrally. There is no sign 

 of flask-shaped mesosomal glands behind the bridle. On the dorsal side of 

 the mesosoma it is possible to make out bundles of longitudinal muscle 

 fibres, at the level of the bridle (Fig. VV133^, В, C). 



The boundary between the mesoma and metasoma is simple and the 

 broad ciliated band begins immediately behind it (Fig. VV133Z?). The 

 metameric part of the metasoma has about 50 pairs of rounded plaqueless 

 papillae, tightly packed together, each containing a single pyriform gland 

 (Fig. W133/4, C). Outside the papillae, on the lateral surface of the meta- 

 soma, the epidermis is very rich in granular gland cells, forming a pair of 

 longitudinal glandular tracts like those of 

 the "taeniaphorous" species (S. taenia- 

 phorum, S. altanticum etc. — see p. 287) 

 (Fig. YV133A). 



The region of the girdles and the post- 

 annular section of the trunk remain un- 

 known, since the body of our only speci- 

 men (which appears to be a male) is torn 

 off in front of the girdles. The genital 

 papillae are rather large (Fig. W133C), 

 but there is no sign of spermatophores. 



The tentacle is 8-4 mm long and the 

 fore-part of the body 1-05 mm. The 

 greatest breadth of the mesosoma is 0-3 

 mm. The metameric section of the meta- 

 soma is 5 mm long and the remainder of 

 what survives of the preannular region 

 26 mm. The overall length of the frag- 

 ment of the animal (including the 

 tentacle) is с 40 mm. 



The smooth lustrous ringed but un- 

 segmented tube is yellow, shading to 

 yellow-brown at the front. The anterior 

 flimsy membranous transparent part of 

 the tube has the end torn away; what is 

 left of this part is some 7 mm long. Grad- 

 ually golden-brown rings appear, a half, 

 a third or a quarter as long as the diameter 

 of the tube. The interspaces between 



С К 



D 



0.2 мм 



Fig. WW 133. Siboglinum zanzibaricum: 

 A-D - successive portions of the tube. 



