POLYBRACHIA 393 



5. Genus Polybrachia Ivanov 



Ivanov, 1952: 379-83, 388-90; Zenkevitch, 1954: 77, 78, 80; Zenkevitch, Birstein and 

 Belyaev, 1954: 68; Hartman, 1954: 184, 185; Ivanov, 1954b: 73, 74, 77, 79; Ivanov, 

 1955a: 177; Ivanov, 1955b: 382, 383; Ivanov, 1955d: 173, 174; Ivanov, 1955e: 224 

 Ivanov, 1956b: 1864, 1868; Ivanov, 1956c: 165; Jagersten, 1956: 238; Kirkegaard, 1956b 

 185, 186; Abrikosov, 1957: 234; Ivanov, 1957a: 431, 435, 439, 442, 449, 460, 461, 470, 475 

 481, 490, 492, 494-7; Ivanov, 1957b: 1139; Vinogradova, 1958: 112; Dajoz, 1958 

 231-3, 236, 237; Fell, 1958: 45, 46; Ivanov, 1958a: 1363, 1369, 1371, 1372; Ivanov, 1960a 

 1528, 1529, 1531, 1538, 1539, 1550, 1552, 1572, 1580, 1583, 1606, 1607, 1620; Ivanov 

 1960c: 6, 11, 12, 14, 24, 36, 37, 43, 57, 59, 66, 69, 75, 92, 94, 114, 199, 203, 215, 230-1, 237 

 Kirkegaard, 1960: 226. 



The protosoma is divided from the mesosoma and the cephalic lobe from 

 the protosoma by a transverse groove. The mesosoma has several secondary 

 annuli in front of the bridle. There are never less than 18 tentacles, but the 

 base of the tentacular crown does not form a complete circle but a horse- 

 shoe. The fore-part of the trunk bears cuticular plaques. The tube is seg- 

 mented with funnel-like frills or collars to each segment. 



There are at least three species: Polybrachia annulata, P. barbata, P. 

 gorbunovi. 



Type species: Polybrachia annulata Ivanov. 



In all likelihood Krampolinum galatheae Kirkegaard belongs to this genus. 

 This species was described by Kirkegaard (1956b), from a collection taken at 

 a depth of 2950-3190 m in the Gulf of Panama in the eastern Pacific Ocean, 

 on the basis of two tubes and a very badly preserved fragment of one indi- 

 vidual, which did not permit any determination of the systematic position of 

 the animal. The delicate pale clear tube is frequently speckled and trans- 

 versely striped. The middle part of the tube has membranous frills, whereas 

 the upper part has a close series of broad funnels (Kirkegaard, 1956b). 

 Kirkegaard believes that this peculiarity of the tube is sufficient to afford 

 grounds for establishing a separate genus within the family Polybrachiidae. 

 The various characters enumerated are, however, all found in species of 

 Polybrachia. It would thus seem that Krampolinum galatheae is a species of 

 this genus, Polybrachia galatheae (Kirkegaard). P. capillaris Southward is 

 better ascribed to Diplobrachia and is so described here. 



Key for the identification of species of Polybrachia* 

 1 (2) There are not more than 20 tentacles. The length of the fore-part of 

 the body is not more than 1 mm, and the breadth not more than 

 0-3 mm. 3. P. gorbunovi (p. 400). 



* Excluding P. galatheae. 



