192 PART П. SYSTEMATIC ACCOUNT 



considerable distance from the third. The first and third girdles are interrup- 

 ted ventrally, the second dorsally (Fig. 100D). The yellowish toothed plate- 

 lets, arranged in a single row in each girdle, are shaped like elongated ovals, 

 and the majority are pinched in at the middle (Fig. 100£). The anterior and 

 posterior groups of teeth are almost equal (Fig 100F) and each consists of 

 6-7 obliquely transverse rows of teeth. The length of a platelet is 10-1 1/x, the 

 breadth up to 4/x. The postannular region of the trunk has not been satis- 

 factorily dissected out. 



The length of the front section of the body is 0-85 mm, the breadth of the 

 mesosoma 0-17 mm, the thickness of the tentacle 0-10 mm. 



The tube is rather hard, brown and ringed. Its front part is flimsy and 

 transparent, with walls that collapse readily, and it is distinctly segmented. 

 Some way back yellow rings gradually appear, eight to a segment. Their 

 length is about one-quarter the diameter of the tube and the light interspaces 

 between them are the same size (Fig. 100G). In the middle part of the tube 

 the segmentation disappears and the rings become closer together, darker in 

 colour and about twice as long, so that the clear intervals between them are 

 mere lines and, not infrequently, neighbouring rings anastomose (Fig. 100//). 

 In the hind part of the tube the pattern of rings becomes less regular, the 

 rings are considerably shorter, often no bigger than those of the anterior end 

 of the tube, their boundaries become uneven, and sometimes neighbouring 

 rings may anastomose with one another by irregular bridges (Fig. 100/). The 

 longest, incomplete, fragments of tube measured 38-40 mm in length. The 

 diameter of the tube was 0-18 mm at the front and 0-13 mm in the middle. 



This species is distinguished from the closely related species (S. ekmani, 

 S. fedotovi and S. plumosum) by the very numerous, closely packed long 

 pinnules and by the posterior constriction of the mesosoma. The lack of any 

 glandular element in the mesosoma and the peculiarities of the tube bring S. 

 pinnulatum close to S. ekmani, while the characteristic thickening of the dorsal 

 ends of the keels of the bridle is reminiscent of S. fedotovi, in which this 

 peculiarity is well marked. Very characteristic of S. pinnulatum is the equal 

 size of the areas occupied by the anterior and posterior groups of teeth on the 

 toothed platelets. 



Material : one specimen and two fragments of tube. 



Locality: off the northern coast of Morotai Island (2°30'N 129°E) in the 

 Moluccas. 



Depth: 260 m. 



