SCLEROLINUM SIBOGAE 419 



"The longest fragment of an animal is 30 mm long, without a posterior 

 end. There are six specimens in which the anterior end can be seen clearly 

 and in all these there are two tentacles, from 0-5 to 2-0 mm long, attached 

 side by side by very narrow basal portions (Fig. HI 625, C, D). The rest of 

 the tentacle is fairly thick, wrinkled and without pinnules. The small 

 cephalic lobe is divided from the rest of the protosoma by a dorsal groove 

 at the level of the tentacle base (Fig. H162C). The separation of protosoma, 

 mesosoma and metasoma is not very clear, as there are no external grooves, 

 and apparently no internal septa. The internal glands seem to be the most 

 useful criterion of their distinction. From the base of the tentacles to about 

 the level of the bridle there are numerous small spherical glands; behind the 

 bridle the glands are still numerous but larger, and after a short distance 

 they give way to two rows of much larger pear-shaped glands. Sometimes 

 an oblique band of muscle is visible between the last two types of glands, 

 perhaps homologous with the meso-metasoma septum of other genera. 

 Using these criteria the total length of the protosoma and mesosoma is 0-5 

 to 0-85 mm. In one specimen the dorsal band of cilia can be seen to begin a 

 little behind the dorsal part of the bridle, some way in front of the start of 

 the largest glands (Fig. H1625). The bridle itself is scarcely raised above the 

 body surface, and its keels are very fine, colourless and often broken up 

 into short curved sections (Fig. HI 625, C). The course of the keels around 

 the body varies from one specimen to another; in some the dorsal points are 

 anterior (Fig. HI 625) to the ventral points while in others they are posterior 

 (Fig. H162D). The keels are sometimes fused (Fig. H162£) and sometimes 

 separate in the mid-line both dorsally and ventrally. 



"Most of the metameric region of the trunk is slightly furrowed longi- 

 tudinally between the two latero-ventral rows of glands. There are no very 

 definite papillae, but there are up to 45 pairs of internal glands, which 

 occupy the first 1-3 to 2-5 mm of the trunk. They do not bear adhesive 

 plaques. The rest of the trunk has small single papillae, each bearing an 

 oval or circular adhesive plaque, with a thickened edge (Fig. H1627 r ), 15 to 

 30/x in diameter. These small papillae are scattered irregularly along the 

 trunk and no large papillae have been seen. Girdles are absent even from 

 the longest specimen, which indicates that the preannular region must be at 

 least 30 mm long, which is an exceptional length in a pogonophore only 

 about 0-07 mm in diameter. Two specimens contain leaf-shaped spermato- 

 phores about 0-10 to 0-15 mm long (Fig. H162G). 



"The tubes are brownish and thin, like those of Siboglinum weberi and 

 S. macrobrachhim with which they are mixed in the collection from Siboga 



