342 



PART II. SYSTEMATIC ACCOUNT 



facing p. 368, there are characteristic distinctions in the relative dimensions 

 of the protosoma, the number of tentacles, the development of the keels of the 

 bridle, the shape and dimensions of the cuticular plaques, the dimensions of 

 the toothed platelets, the number of metameric papillae and of the papillae 

 of the zone of thickening, the dimensions of the spermatophores, etc. 



Material: many tubes, some with animals. 



Locality: the Bering Sea to the east, southeast and south of Cape Olyu- 

 torski (60°N 171°E), and also to the east of the Komandorski Islands 

 (55°N 166°E). Depth: 1693-4811 m. 



3. Heptabrachia subtilis Ivanov (Figs. 138-41) 



Ivanov, 1957a: 465-9, 491,494, 496-8, Figs. 35-40; Dajoz, 1958: 236; Ivanov, 1960c: 

 6, 11, 12, 23, 92, 93, 199, 200, 203, 207-211, 214, 263. 



Only two females of this species are 

 known. The slender fore-part of the body 

 is almost cylindrical (Fig. \38A, B). The 

 protosoma is half the length of the meso- 

 soma and the sharp groove between them 

 runs straight across the ventral side and 

 arches forward dorsally. The elongated 

 cephalic lobe, which is not divided from 

 the protosoma, is slightly flattened dorso- 

 ventrally. In front of the base of the ten- 

 tacular crown lies a broad depression in 

 the protosoma but this is most probably 

 an artefact resulting from the strong con- 

 traction of the base of the tentacular crown 

 into the body at the moment of fixation. 

 The tentacles are long and thin. Their 

 number has been studied only in sec- 

 tions, in which seven were found in one 



Fig. 138. Heptabrachia subtilis: Front end of a female. 

 A -in dorsal, and, В - in ventral view. 

 с - cephalic lobe ; со - dorsal ciliated band ; /- keel of 

 the bridle ; ms - mesosoma ; p - cuticular plaques ; pa - 

 papilla with pyriform glands visible by transparency; 

 ps - protosoma ; s 1 - groove between the protosoma and 

 the mesosoma ; s 2 - groove between the mesosoma and 

 the metasoma ; sv - ventral sulcus ; t - tentacles. (After 

 Ivanov, 1957a.) 



