SIBOGLINUM VINCULATUM 203 



Material: 30 fragments of tubes amongst which were three with animals in 

 them. 



Locality: the Pacific Ocean to the east of the northern part of Honshu, 

 Japan. 



Depth: 1660 m. 



7. Sibogliniim vinculatum Ivanov (Figs. 106-7) 



Ivanov, 1960c: 5, 12, 16, 19, 97, 125, 145-8, 151, 196, 264, Figs. 87, 106-7. 



In trial dredgings made by R.V. Vitya£ in January, 1958, in the Tasman 

 Sea, near the coast of New Zealand, at depths of 1740 and 1225 m, were 

 found two white ringed tubes, recalling those of S. cinctutum (p. 207) and 

 S.frenigerum (p. 213). In both tubes were discovered animals undoubtedly 

 belonging to no known species. One of these individuals, which turned out 

 to be a male, was considerably larger than the other, which, to all appearances, 

 was a young female. The proportions of the various parts of the body in the 

 male seemed, at first glance, to differ considerably from those of the female, 

 but this difference, in all likelihood, could be ascribed to the female's having 

 been fixed in a strongly contracted condition. The most characteristic 

 feature of this species is the presence of three annular grooves between the 

 base of the tentacle and the bridle, giving it a cross-banded appearance, and 

 it is to this that S. vinculatum owes its name [Latin vinculum, a band, hence, 

 vinculatum, banded]. 



The length of the fore-part of the body in the male is seven times, and 

 in the female five times the breadth (Fig. \%A, В, C). The second of the 

 three annular grooves corresponds in position to the boundary between the 

 protosoma and the mesosoma. On the ventral side it arches a little forward, 

 while on the dorsal side it has a small median notch, pointing backwards. 

 The last annular groove has a similar median notch on the ventral side, and 

 the first groove lies immediately behind the base of the tentacle (Fig. 

 \06A, В, C). The large, somewhat dorso-ventrally flattened, cephalic lobe is 

 shaped like an equilateral triangle, and through its integument the median 

 and lateral cephalic blood vessels can faintly be made out (Fig. 1065). The 

 comparatively stout, cylindrical tentacle is furnished with a double, alter- 

 nating row of pinnules, 75-80/x long (Fig. 106A, D), within which the affer- 

 ent and efferent capillaries may readily be observed (Fig. 106E). 



The cylindrical mesosoma has a narrow median ventral furrow in front of 

 the bridle, which latter lies in the centre of the fore-part of the body. Its 

 rather stout, yellowish keels are fused ventrally and gradually taper towards 



