312 PART II. SYSTEMATIC ACCOUNT 



the bridle, the unsegmented, very fibrous tube, and the well-differentiated 

 dorsal shields in the postannular region of the trunk. The tube of S. exile 

 resembles that of S. weberi (inhabiting the Indo-Malaysian region), 5. 

 hyperboreum (from the North Atlantic) and S. tenue and S. pusillum (both 

 from the Pacific Ocean). In other respects, however, it is considerably 

 different from all these species. 



Material : seven tubes, five with animals, all females. 



Locality: Vityaz 1 station 4543 (31st cruise): Indian Ocean near the 

 southern tip of Sumatra to the west of the entrance to Sunda Strait. 



Substratum: muddy sand. 



Depth: 626 m.] 



[36. Siboglinum sumatrense sp. nov. Ivanov (Figs. TT133, UU133) 



One tube containing an animal and fragments of empty tubes of this 

 species were found together with S. exile sp. nov. off the coast of southern 

 Sumatra in the Indian Ocean. 



The fore-part of the body is cylindrical and the protosoma clearly defined. 

 The length to breadth ratio of the fore-part is 9 : 1. The protosoma runs 

 imperceptibly into the small brief conical cephalic lobe. The thick ten- 

 tacle is attached one-third of the length of the protosoma from its tip 

 (Fig. ТТ133у4). It bears rather dense pinnules (c. 70/x long) arranged 

 apparently in two rows (Fig. TT133C). 



The bridle lies one-third of the way along the mesosoma. Its thin keels are 

 colourless and neither taper nor thicken towards the ends. They meet neither 

 dorsally nor ventrally (Fig. ТТ133Л, B). The mesocoele is filled behind 

 the bridle with flask-shaped glands. There is nothing to remark about the 

 boundary between the mesosoma and metasoma (Fig. ТТ133Д B). 



The ventral sulcus of the metasoma is sharply defined. The metameric 

 papillae are poorly differentiated — within the lateral ridges which bound the 

 ventral sulcus paired metameric pyriform glands can be distinguished, 

 which in the anterior metameric region stick up just a little as slight humps 

 (Fig. TT1335). There are no cuticular plaques. 



There are two girdles lying close together. The toothed platelets, 13-14/x 

 long, are uniserial (Fig. TT133Z)). They are somewhat narrower at the 

 front end where they bear the small anterior group of teeth. This part is 

 only a third the length of that which bears the posterior teeth (Fig. TT133£). 



The postannular region is well differentiated, bearing small ventral 

 papillae and dorsal glandular shields at rather short regular intervals (Fig. 

 TT133.F). The former are furnished with a transparent thickening of the 



