376 PART II. SYSTEMATIC ACCOUNT 



A cortical zone free of sperm extends from the base of the filament down 

 the edges of the spermatophore, not, however, reaching the pointed end, 

 which is completely filled with sperm. The filament begins as a large tri- 

 angular membrane which rapidly tapers into the stout basal part of the 

 filament proper. The spermatophores are 0-25 mm long with a maximum 

 breadth of 0-04 mm. 



The front part of the flexible yellow-brown ringed tube is colourless, 

 transparent, membranous and limp, with segments three and a half times as 

 long as the tube is broad. Each segment has a few thin transverse fibres in the 

 hindmost part, then gradually in each segment six or seven brownish rings 

 appear (Fig. 1515). The greater part of the tube lacks perceptible boundaries 

 between segments and possesses fibrous, muddy-brown rings whose length 

 does not equal the diameter of the tube (Fig. 151C, D). The tube may be up 

 to 95 mm long, with a diameter of 0-17-0-22 mm at the front end of the 

 ringed part. 



Material: many tubes, some with animals. 



Locality: the Japan Trench to the east of Honshu. 



Depth: 7450-7520 m. 



2. Diplobrachia belajevi Ivanov (Fig. 152) 



Ivanov, 1960c: 5, 97, 220, 223-6, 265, Figs. 87, 152. 



A second species of Diplobrachia was found in the Indian Ocean a little to 

 the east of Rodriguez Island by R.V. OF in 1956. The material, consisting of 

 fourteen small fragments of tubes, was collected in a trial dredging taken at a 

 depth of 580 m, and three incomplete animals were found in the tubes. This 

 species, named after Dr. G. M. Belyaev, possesses a comparatively short, 

 somewhat dorso-ventrally flattened fore-part of the body, whose length is 5-6 

 times its breadth (Fig. 152Д B). A simple annular groove defines the forward 

 limit of the mesosoma in front of the bridle, and the protosoma in front of it 

 is rather large, a little narrower than the mesosoma at its hind end but 

 widening out forwards before passing imperceptibly into the broad, tri- 

 angular or conical, more or less round-ended cephalic lobe (Fig. 152/4, B). 

 The long equal tentacles are attached side by side in the middle of the 

 protosoma (Fig. 152^4). The pinnules on the tentacles have not been pre- 

 served. The bridle is situated in the front part of the mesosoma. The basal 

 axes of its keels are strongly developed, broad, colourless and irridescent 

 under incident light. On the ventral side of the body, arranged in a single 

 row behind the axes and touching them, are the cuticular rodlets (Fig. 



