160 PART II. SYSTEMATIC ACCOUNT 



colourless and transparent, with walls which collapse rather easily (Fig. 92B). 

 Towards the hind end also, the rings vanish and the tube becomes semi- 

 transparent (in preserved material generally of a yellowish tint), but, in con- 

 trast to the front end, the walls here are very firm, and the surface is covered 

 in weak longitudinal ribs or folds. The biggest known fragment of tube 

 measures 25 cm and the anterior membranous part of another specimen 

 reaches 3 cm in length. The diameter of the tube near the front end varies 

 between 0-5 and 9-62 mm. 



Material: part of 16 individuals, all incomplete, and a few dozen torn-off 

 empty tubes. 



Localities: the sub-littoral and semi-abyssal zones of the western and 

 northern parts of the Okhotsk Sea in depths of 1 19-572 m. One example was 

 taken also from farther east, south of Kamchatka, in abyssal depths (2532 m). 

 In addition two fragments of empty tubes were discovered in the abyssal zone 

 of the Japan Sea at 2850 m depth. 



2. Oligobrachia ivanovi E. C. Southward (Fig. A92) 

 E. С Southward, 1959; 38, 439-41, 444, Fig. 1. 



[This species was unknown to Ivanov at the time of publication of the 

 Russian edition of this book, and the following description is quoted almost 

 verbatim from Dr. Southward's original description. In order to bring this 

 description into line with the others in this monograph I have taken the 

 liberty of transposing paragraphs and sentences so that the various parts of 

 the body shall be described in the same order, and to the same end I have 

 altered the nomenclature slightly. I am grateful to Dr. Southward and to the 

 Council of the Marine Biological Association of the United Kingdom for 

 granting permission to reproduce both the description and the illustration 

 — D.B.C.] 



"Only one specimen of this species has been found . . . collected on 28 

 November, 1958, at 48°26'N 10°8'W on a cruise of R.V. Sarsia. It has been 

 named after Prof. A. V. Ivanov. The animal is 95 mm long, and since only 

 10 mm of the postannular region of the trunk is present the complete animal 

 must have been considerably longer. Its diameter is about 0-5 mm and its 

 colour is greenish brown with brown tentacles and red blood. There are 

 7 tentacles, coiled together, which are 12 mm long. Each has a double row of 

 pinnules along the inner side (the length of the pinnules being about equal 

 to the diameter of the tentacle) and a band of brown spots on the outer side 

 (Fig. A92D). The tentacles are joined to the protosoma in a circle just in front 

 of a slight transverse groove (Fig. A92B). The protosoma is about 0-8 mm 



