370 



PART II. SYSTEMATIC ACCOUNT 



?; ; 



The spermatophores are flat and leaf-shaped, about 1 mm long by 0-3 mm 

 broad. The filamentary end is broad and rounded, the opposite end taper- 

 ing evenly to a point (Fig. 146). The filament begins by bending down 

 towards the spermatophore as a broad basal plate, before dwindling rather 

 quickly into the ribbon-like proximal part of the filament. The surface of 



the very firm, dark tube of C. auriculata is 

 smooth and the walls are structureless and 

 slightly translucent. There are neither rings 

 nor segmentation (Fig. 147), except that on 

 a few fragments of moderate diameter very 

 faint traces of segmentation were detected. The 

 biggest fragments of tubes reached 70 mm in 

 length, but the total length must be much more. 

 The diameter of the thickest fragment is a little 

 more than 1 mm. 

 Material: one male and 13 scraps of tube. 

 Locality: New Britain Trench, to the south- 

 west of Bougainville Island in the Coral Sea. 

 Depth: 7974-8006 m. 



Fig. 147. Cyclobrachia auri- 

 culata : part of tube. 



3. Genus Diplobrachia Ivanov, 1960 



Ivanov, 1960c: 6, 24, 106, 107, 114, 199, 219-20, 252. 



In a trawl-haul taken by R.V. Vityaz? in the spring of 1957 in the region of 

 the Japan Trench at a depth of 7500 m were found numerous slender brown 

 tubes of a pogonophore, very like those of Siboglinum ; so like them, in fact, 

 that they were so described in the log. They were found, however, to belong 

 to a new genus, Diplobrachia, which, without doubt, belongs to the order 

 Thecanephria. An unexpected and very distinctive feature of this genus is 

 the possession of two to four tentacles. Its thecanephrial affinities may be 

 judged from the development of transverse, ventral rows of papillae, bearing 

 cuticular plaques, on the postannular section of the trunk, and from the 

 characteristic leaf shape of the spermatophores, while the absence of any 

 connexion between the tentacles and the distinctive protosoma suggest that 

 amongst the Thecanephria this animal lies nearest to the Polybrachiidae. In 

 spite of the reduction in numbers of the tentacles Diplobrachia scarcely 

 merits the erection of a separate family, since it is distinguished from 

 typical Polybrachiidae by but few characters. The genus Diplobrachia may 



