158 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 22 



Genus MELINNEXIS Annenkova, 1931 



This genus is characterized as follows: Oral tentacles are of 2 kinds, 

 including a thick, papillated, proboscislike unpaired one, and many short, 

 slenderer ones. The tentacular membrane is entire ; glandular bands are 

 absent. Branchiae number 4 pairs and are subulate. The lateral margins 

 of segments 2 to 5 are raised, as in Melinna, but dorsal, postbranchial 

 hooks are absent. A dorsal transverse fold is feebly visible but lacks 

 denticulations. Segments 2 to 5 are provided with deeply embedded, 

 slender, distally pointed setae. Longer, slenderer, notopodial setae are 

 present from the third segment and occur on 14 segments. Uncini are 

 present from the second one and continue back throughout the body. 



The thorax consists of 17 segments and the abdomen of many. The 

 body terminates posteriorly in a pair of long, anal cirri. Nephridia occur 

 on segments 4, 6, 7 and 8 ; the anterior ones have a much longer shank 

 than posterior ones. 



Melinnexis was erected with type M. arctica Annenkova (1931, p. 

 269) from Franz Joseph Land in the Arctic Ocean. It has remained 

 known largely through the investigations of Soviet scientists. Uschakov 

 (1955, pp. 363-364) has summarized the two best known forms, M. 

 arctica and M. annenkovae Uschakov, and added a third, M. somovi 

 ( 1957, p. 1672) also from the Arctic in abyssal depths. At least 2 others, 

 from more southern latitudes, may be congeneric. 



Melinnexis monocera (as Melinna monocera Augener, 1906, p. 117) 

 from the Lesser Antilles, has been referred to this genus by Annenkova 

 (1931, p. 270). Another is Melinnexis tentaculata (Treadwell) from 

 deep water off the Hawaiian Islands (Hartman, 1956, p. 296). 



Moyanus Chamberlin (1919, p. 451) with type M. explorans Cham- 

 berlin (1919b, pp. 452-455, pi. 77, figs. 11, 12) from off Peru in 2222 

 fms, is almost certainly another species of the same genus. It is large, 

 measures 114 mm long and 4 mm wide, and consists of 81 segments. The 

 proboscislike organ is flattened dorsoventrally, and other tentacles are 

 much slenderer and shorter. The dorsal membrane is on the fourth seg- 

 ment and not denticulate. Nuchal spines are absent. Branchiae number 

 4 pairs, are inserted on a common base, and all are of one kind. The 

 thorax consists of 15 setigerous segments, but notopodia of the first few 

 segments are very obscure. 



