SIBOGLINUM CAULLERYI 111 



also lacking rings, is structureless and transparent, but it has comparatively 

 firm unbending walls. The longest fragment of tube reaches 20 cm, but 

 amongst a great number of tubes only one was found which was not torn 

 across. The length of the hindmost transparent portion is therefore uncertain. 

 In a few cases it extended for 2 cm before the break. The front membranous 

 part of the tube reaches not less than 2-5 cm. 



Caullery (1944), in describing the tube of S. weberi, stated that it was 

 completely cylindrical and untapered. In S. caulleryi, as in all other Pogono- 

 phora, it tapers towards the hind end, though very gradually. Thus a frag- 

 ment 20 cm long measured 0-3 mm in diameter at the front end and 0-2 mm 

 at the hind end, i.e. a taper of 0-05 mm in 10 cm, or 5/x/cm. Very nearly the 

 same result has been obtained from measurements on other fragments. All 

 the broken tubes are almost equal in diameter, measuring 0-2-0-3 mm at the 

 front end. 



The major specific characters distinguishing S. caulleryi from other 

 species are as follows : the arrangement of the pinnules in a single row, the 

 dorsally curved groove between the protosoma and the narrow dorsal ciliated 

 band, the five mid-ventral papillae of the zone of thickening, and some 

 features of the tube. One of the species closest to S. caulleryi, to all appear- 

 ances, is S. japonicum (p. 200). 



Material : many tubes, some with animals and some empty. 



Localities: S. caulleryi is a typical representative of the benthic fauna of the 

 Sea of Okhotsk, occurring in massive numbers to the east and northeast of 

 the Shantarski Islands (55°N 137°E) at a depth of 90-150 m. It occurs also 

 in Sakhalin Gulf (54°N 141°E) at 22-3 m, to the south of Tauiskaya Bay 

 (59°N 150°E) at depths of 71 and 168 m, to the east of Cape Elizaveti 

 (54°N 143°E — Cape Yelizavety in some atlases) at depths of 365 and 1518 m 

 and near the west coast of Kamchatka at 355 m, all localities in the Sea of 

 Okhotsk. A typical individual of the species was also taken in the Kuril- 

 Kamchatka Trench at a depth of 8164 m. From these figures can be seen the 

 enormous bathymetric range of S. caulleryi. 



11. Siboglinum pusillum Ivanov (Fig. 114) 



Ivanov, 1960c: 5, 126, 145, 158-60, 162, 197, 264, Figs. 87, 114. 



A characteristic species of the northwestern part of the Pacific Ocean 

 appears to be S. pusillum, collected in rather large numbers by R.V. Vityaz 1 

 in 1953 to the east of the northern Kuril Islands. Specimens of this species 

 were at first mistakenly ascribed to S. minutum (Ivanov, 1957a) from the 



