190 PART II. SYSTEMATIC ACCOUNT 



Skagerrak and Southward had abundant material from southwest of Great 

 Britain. 



Localities: Skagerrak, and also from southwest of Great Britain. 



Depth: 340-1250 m. 



3. Siboglinum pinnulatum Ivanov (Fig. 100) 

 Ivanov, 1960c: 5, 18, 19, 96, 105, 126, 134-6, 140, 142, 145, 170, 196, 265, Figs. 87, 100. 



One specimen of this species was taken in a trial dredging made in August, 

 1957, by R.V. Vitya£ off the north coast of Morotai (in the Molucca Islands) 

 at a depth of 260 m. 



The comparatively short fore-part of the body bears characteristic con- 

 strictions behind the bridle and on the rear edge of the mesosoma (Fig. 

 100/4). The boundary between the protosoma and the mesosoma is distinctly 

 visible in front of the bridle, and the protosoma narrows noticeably from this 

 point towards the front end, where it passes imperceptibly into the dorso- 

 ventrally flattened, triangular cephalic lobe. The extraordinarily stout 

 tentacle is covered with numerous circular wrinkles (probably in consequence 

 of strong contraction upon fixation) and very densely furnished with long 

 pinnules (up to 0-15 mm long) arranged in a double row (Fig. 100/4). The 

 general appearance of the tentacle with its numerous pinnules rather recalls 

 that of S. rveberi as figured by Caullery (1944, Fig. 10), but in S. pinnulatum 

 the pinnules start almost at the base of the tentacle. 



A median furrow runs between a pair of ventral swellings which lie on the 

 mesosoma in front of a well-developed bridle. The brown keels of the latter 

 are fused together ventrally and become gradually thicker towards the dorsal 

 ends (Fig. 100у4, В). Behind the bridle, on the dorsal side, stretches a 

 narrow median groove. 



The metameric part of the preannular region of the trunk has a row of 

 large papillae on each side of the deep ventral sulcus (Fig. 100^4.) There are 

 three girdles of toothed platelets, the first two situated close together at a 



Fig. 100. Siboglinum pinnulatum: A - front end of the body from the side; В -the same from the 

 dorsal side ; С - the ventral fusion of the keels of the bridle ; D - part of the metasoma with the 

 girdles in ventral view; E - part of a girdle of toothed platelets ; F - a toothed platelet from the side; 

 G - front part of tube ; H - middle part of tube ; / - hind part of tube. 



an - girdles of toothed platelets ; с - cephalic lobe ; со - dorsal ciliated band ; da - anterior teeth ; 

 dp - posterior teeth ; /- keel of the bridle ; ms - mesosoma ; pa - papillae ; pi - pinnules ; ps - proto- 

 soma ; s l - groove between protosoma and mesosoma ; x 2 - groove between mesosoma and metasoma ; 

 5 3 - pretentacular groove ; / - tentacle. 



