306 PART II. SYSTEMATIC ACCOUNT 



The brown flexible thin-walled tube is segmented at the front end and 

 ringed. Its surface is smooth and lustrous. The anterior filmy portion of the 

 tube is transparent and colourless, but it has clearly defined segments. Then 

 the tube becomes brown, and within each segment clear slightly raised rings 

 appear, at first only in the two ends of the segment and then gradually 

 appearing also in the middle (Fig. 001335). The fully formed segments 

 may have seven to ten rings each, but the most usual number is eight. The 

 second, third and fourth rings in each segment are frequently very irregular. 

 In the middle part of the tube the segments disappear, the rings become 

 considerably longer and denser, brown-grey and homogeneous. They are 

 a third to a half as long as the tube is wide. The narrow interspaces between 

 the rings are transparent, with a golden glitter (Fig. 00133Z)). The tube 

 retains this character for a great length. Towards the hind end of the tube 

 the rings gradually pale and the clear interspaces grow longer in comparison 

 with the length of the rings (Fig. 00133£). In the hindmost part of the 

 tube the very delicate rings possess diffuse edges and become very short, 

 so that they look like narrow belts. The interspaces are here rather long 

 (Fig. 00133/4. 



S. ceylonicum belongs to the group of species with a bipectinate tentacle, 

 a pretentacular groove, three girdles, a strongly developed anterior tooth- 

 group on the toothed platelets and a segmented tube. Others of this group 

 are S. pinnulatum, S.fedotovi, S. ekmani, S. silone sp. nov. and S. plumosum. 

 Most of all this new species recalls S. pinnulatum, from the western part of 

 the Pacific Ocean. In the latter each segment of the tube also has eight rings. 

 S. ceylonicum is like S. fedotovi (known from the northwestern part of the 

 Pacific Ocean) in the nature of its toothed platelets. It may readily be dis- 

 tinguished from all these species, however, by the following characters : 



1. The presence of a pretentacular glandular girdle; 



2. The characteristic curve of the keels of the bridle; 



3. The very thick tentacle; 



4. The somewhat greater development of the anterior group of teeth on 

 the toothed platelets. 



Material: six tubes with more or less complete animals, four tubes with 

 parts of animals and six empty tubes. 



Locality: Vityaz' station 4618 (31st cruise): between Ceylon and the 

 Maldive Islands. 



Substratum: grey mud and Foraminifera. 



Depth: 1920-2970 m.] 



