SIBOGLINUM FEDOTOVI 193 



4. Siboglinum fedotovi Ivanov (Figs. 6, 84A, 101, 102) 



Ivanov, 1957a: 449, 453-9, 491, 495-7, Figs. 23-7, 59; Ivanov, 1960a: 1541, 1612, Figs. 

 1388, 1445, 1465; Ivanov, 1960c: 5, 12, 14, 92, 96, 105, 126, 134, 136, 137-40, 142, 145, 

 154, 167, 188, 196, 269, Figs. 6, 65, 87, 101-2. 



S. fedotovi is one of the few Pogonophora characteristic of the south- 

 western parts of the Bering Sea. This species is in the collection of R.V. 

 Vityaz? which was made along the line of stations east of Kamchatka and north 

 of the Komandorski Islands. 



The comparatively great length of the fore-part of the body is striking, 

 reaching seven to ten times its breadth (in individuals fixed inside the tube), 

 though the protosoma and cephalic lobe together account for only about one- 

 fifth of this length (Fig. 10Ы, B). The protosoma is reduced to a mere girdle, 

 whose breadth is considerably greater than its length. It is divided from the 

 mesosoma by a circular groove, while another groove cuts it off from the 

 cephalic lobe. The latter is somewhat bigger than the protosoma and a little 

 thickened, with a pointed tip. Around its periphery, on the dorsal side, 

 single-celled glands are visible by transparency (Fig. 1015). The tentacle is 

 attached to the front edge of the protosoma and bears along most of its 

 length two dense rows of fine, long pinnules (Fig. 1015). In fixed specimens 

 it is often strongly contracted. 



The bridle is placed near the front of the cyclindrical mesosoma (Fig. 

 10Ы, B). Its keels are joined together ventrally, but just fail to meet dorsally, 

 a fact which often can be observed only under the microscope. They are 

 generally the same thickness throughout their extent, but sometimes they 

 may even become thicker towards the dorsal ends. Immediately behind the 

 bridle lie a pair of transverse glandular tracts, tinted brown and situated 

 latero-ventrally. 



The metasoma is delimited by a circular groove, which curves slightly 

 backwards on the ventral side, while the rather narrow dorsal ciliated band 

 begins immediately in contact with it at the front end of the trunk (Fig. 

 1015). The metameric adhesive papillae are rounded, lacking in plaques and 

 becoming larger in size and irregular farther back. In one individual studied 

 there were about 80 pairs. In the male the larger genital papillae are situated 

 in front of the first pair of the series (Fig. 10Ы). 



In the original description of S. fedotovi (Ivanov, 1957a, pp. 453-9) I 

 stated erroneously that this species was peculiar in having only one girdle of 

 toothed platelets. I was, in fact, observing the hindmost of the three girdles 

 which it actually possesses, as I have discovered more recently in examining 



