SIBOGLINUM TAENIAPHORUM 261 



they are more disorderly in disposition. In the zone of thickening three large 

 conical transparent papillae lie in the mid-ventral line one behind the other 

 (Fig. \29A). Two girdles of toothed platelets lie on rather stout muscular 

 ridges and both are interrupted on the ventral side only. Immediately in 

 front of the first girdle lie three conical ventral papillae, one behind the other 

 (Fig. 1295). The pale yellow, toothed platelets, arranged in three, four or in 

 places in five rows, are elongated ovals, without any constriction in the middle 

 (Fig. 129C). They measure 11-5-13/x long by с. 2-5/л wide, and the front 

 group of teeth is rudimentary (Fig. 129D). The very long postannular region 

 of the metasoma is covered in numerous scattered button-like groups of 

 epidermal gland cells. A metameric series of papillae extends down the ventral 

 side, and opposite each of them, on the dorsal side, is a glandular area of 

 irregular outline, not distinguishable in appearance from the scattered 

 glandular warts (Fig. 1295), but nevertheless representing extremely weakly 

 developed dorsal glandular shields. 



Our complete specimen has the following dimensions : length of the ten- 

 tacle, с 15 mm; fore-part of the body, 3-1 mm by 0-36 mm; breadth of the 

 middle part of the metasoma, 0-23 mm; length of the preannular section, 

 34 mm; length of postannular section, 17 mm; overall length of the body, 

 69-1 mm. 



In the living animal a number of organs show up coloured or opaque 

 against a colourless and semi-transparent background. Thus the blood 

 vessels filled with red blood may be seen in the mesosoma, the metasoma and 

 the tentacle. The many-celled pyriform glands of the mesosoma and meta- 

 soma show whitish through the integument, while the glandular tracts and 

 longitudinal ribbons of the epidermis are yellowish, as are the ovary and eggs 

 in the oviduct. The wart-like groups of epidermal gland cells of the metasoma, 

 in both the preannular and postannular parts are a lustreless creamy white. 

 The conical ventral papillae, in the zone of thickening, in front of the girdles, 

 and in the postannular section of the trunk, are all, by contrast, glassily 

 transparent. 



The tube is elastic, white, translucent and rather stout-walled. The front 

 part is whitish with a faint dirty-brown tinge and distinctly segmented, with 

 segments only a little longer than the diameter of the tube. Here and there 

 in the walls of the tube are soft transverse fibres (Fig. 13CL4). Then the fibrous 

 structure becomes denser and a little coarser, and the succeeding part of the 

 tube has white semi-transparent rings, many of them short and broken or 

 irregularly shaped. The intervals between them are not large, but so trans- 

 parent that the rings on the other side of the tube can easily be seen through 



