404 PART II. SYSTEMATIC ACCOUNT 



lacks secondary rings. In front of the bridle there are two longitudinal dermal 

 lappets or folds which in front turn onto the dorsal side of the protosoma 

 where they fuse with each other. In known species there are 78-268 tentacles 

 arranged on a horse-shoe-shaped base. The segmented tube has a funnel-like 

 frill on the front edge of each segment, covered with a thin felt-like layer of 

 rather coarse fibres. 



Type of the genus: Galathealinum bruuni Kirkegaard. 



Three species have been described — Galathealinum bruuni Kirkegaard, 

 G. brachiosum Ivanov and G. arcticum Southward.] 



Key for the identification of the species of the genus Galathealinum 



1 (2) Each metameric papilla bears a single cuticular plaque; there are no 



large papillae of the second order, bearing several plaques each, on the 

 metameric section of the metasoma. The hind part of the mesosoma 

 has a mid-ventral furrow. The dorsal ends of the keels of the bridle 

 meet or fuse. The cephalic lobe is triangular, truncated at the tip. The 

 plaques on the metameric papillae are about 30/a across, those on the 

 non-metameric papillae about 50-65//.. The fibres of the external 

 layer of the tube are 1-2/u. thick. 3. G. arcticum (p. 414). 



2 (1) There are large papillae of the second order in the metameric section 



of the trunk, each bearing several cuticular plaques. There is no mid- 

 ventral furrow in the hind part of the mesosoma. The dorsal ends of 

 the keels of the bridle do not meet. 



3 (4) The metameric papillae of the second order for the most part bear 



two plaques. The plaques of the metameric papillae are about 40/x 

 across, those of the non-metameric papillae about 60/x. The fibres of 

 the external layer of the tube are 2-4/a thick. 1. G. bruuni (p. 404). 



4 (3) The metameric papillae of the second order bear two to ten plaques 



each. The plaques of the metameric papillae are 60-90^ across, those 

 of the non-metameric papillae about 80/x. The fibres of the external 

 layer ofthe tube are 7-1 2/x thick. 2. G. brachiosum (p. 407). 



/. Galathealinum bruuni Kirkegaard (Figs. 161-2) 



Kirkegaard, 1956a: 79-82, Figs. 1, 2; Kirkegaard, 1956b: 186, Fig. 4; Ivanov, 1957a: 

 431, 460, 461, 492, 494, Fig. 59; Jagersten, 1957: 76; Dajoz, 1958: 236, 237, Fig. 6; 

 Ivanov, 1960a: 1611; Ivanov, 1960c: 6, 24, 96, 239-11, Figs. 161-2; Ivanov, 1961c: 

 1382-4, Fig. 6. 



