SIBOGUNUM DEBILE 273 



collected near the Solomon Islands, but differs in the shape of the bridle, 

 the number of rows of pinnules on the tentacle and the rings on the tube. 

 S. pinnulatum Ivanov is another species with much in common with S. 

 macrobrachium, but again they differ in the arrangement of the pinnules, 

 the lack of a pretentacular groove in S. macrobrachium, the form of the bridle, 

 and the thickness and arrangement of the rings on the tube. The large sperma- 

 tophores resemble those of S. fedotovi Ivanov and the tube, though smaller, 

 also resembles that of S.fedotovi." 



Material: 18 occupied tubes plus at least 20 more tubes, some occupied. 



Locality: Java Sea: Siboga station 212 (5°54'S 120°19'E). 



Depth: 462 m.] 



[27. Siboglinum debile Southward (Fig. C133) 

 Southward 1961b: 7-8, 21, Fig. 3. 



This is another species of the Siboga material, originally included in 

 S. weberi. The following description is transcribed from Southward (1961b), 

 by kind permission of the author and the publisher, E. J. Brill. 



"The animals are up to 14 mm long, with a tentacle up to 1-1 mm long and 

 30 to 50/x in diameter. There is one row of rather long pinnules (60 to 80/*) 

 on the tentacle. The fore-part of the body varies in length from 0-7 to 1 -6 mm 

 and the ratio of its length to its diameter varies from 5 : 1 to 11 : 1. The 

 cephalic lobe is flattened dorso-ventrally and ends in a point; the surface of 

 the protosoma and mesosoma seems to be smooth, without any definite 

 grooves (Fig. С133у4, В). The bridle is a well-marked ridge, cross striated in 

 appearance, surmounted by pale yellow keels which join in a point on the 

 ventral side but are well separated on the dorsal side (Fig. C1335). 



"The mesosoma and metasoma are separated by a very shallow transverse 

 groove ; the papillae and ventral sulcus of the metameric region are rather 

 indefinite and extend for 1-3 to 2 mm. The whole preannular region is 

 6-5 to 11 mm long and seems to lack all but metameric papillae. There are 

 two girdles which lie fairly close together (0-05 to 0-25 mm apart), each of 

 which is made up of one or two irregular rows of toothed platelets (Fig. 

 C133C). About 5 mm of the postannular region has been seen but details of 

 it could not be made out. All the specimens seem to be immature. 



"The tubes are whitish but transparent, with thin, limp, unringed walls. 

 The biggest is 4 cm long, and the diameter varies from 0T to 0-135 mm, but 

 it is difficult to measure accurately, as most of the tubes are flattened and 

 twisted to a much greater extent than is usual for Siboglinum tubes. 



