222 PART II. SYSTEMATIC ACCOUNT 



similarity of the tubes of the two species. The description of S. pusillum is 

 based on five specimens. 



The fore-part of the body is slightly compressed from side to side, and its 

 length exceeds the breadth of the mesosoma seven or eight fold (Fig. 114Д 

 В, C). The more or less triangular cephalic lobe is slightly flattened dorso- 

 ventrally. Behind the base of the tentacle runs an obvious annular groove, and 

 the tentacle itself is attached a little to the right of the mid-ventral line. The 

 rather short pinnules, present in the middle and distal parts of the tentacle, 

 are arranged in a single row (Fig. 114D). In one individual they were found 

 to be exceptionally short, rather few and far between, and developed only on 

 the distal half of the tentacle. The keels of the well-developed bridle, looking 

 like delicate dirty-brown bands, are fused together ventrally, but the dorsal 

 ends are a considerable distance apart (Fig. 1145). Behind the bridle in a few 

 individuals it is possible to observe weakly developed glandular portions of 

 the integument, forming rudiments of a glandular girdle. The back edge of 

 the mesosoma arches slightly forwards on both dorsal and ventral sides. 



A pyriform gland is visible inside each of the numerous small rounded 

 paired papillae of the metasoma, and the ventral sulcus between them is 

 comparatively narrow, limited by the latero-ventral ridges on which the 

 papillae stand (Fig. 114у4). The dorsal ciliated band is also narrow (Fig. 

 1145). The greater part of the preannular region of the metasoma remains 

 unknown. There are two girdles lying close together and each bearing but 

 one row of elongated toothed platelets (Fig. 114£), which are evenly rounded 

 at the ends and, for the most part, bent. The front end of each platelet is a 

 little narrower than the back, but the front group of teeth is only a little 

 less developed than the hind group (Fig. IIAF). The yellowish platelets are 

 11— 12/x long. The very long and slender postannular region of the trunk is 

 furnished with small, button-like, dorsal, glandular shields, arranged in a 

 metameric series at a considerable distance from one another. The ventral 

 papillae opposite the shields are conical and lack cuticular thickenings or 

 plaques (Fig. 114G). 



Measurement of the parts of the body in four individuals gave the follow- 

 ing results: length of the tentacle, с 4 mm; length of the fore-part of the 

 body, 0-6-0-85 mm; breadth of the mesosoma, с 0-1 mm; length of the pre- 

 annular region of the metasoma, с 20 mm; length of the postannular region, 

 20-26 mm; overall length of the body, including the tentacle, 43-49 mm. 



The filmy transparent, slightly greyish fore-part of the tube has transverse 

 fibres sticking up above the surface of the tube wall. The very front part of 

 the filmy section has very sparse, soft fibres, but farther back they increase 



