"Aglaophamus posterobranchus, new species
(Plate 25)
Records:
1:19 sta. 333 ( 1); 8: 5 sta. 727 ( 1);
8: 7 sta. 735 ( 4); 8: 9 sta. 691 ( 1); 9: 9 sta. 260 ( 2);
9:10 sta. 250 ( 3); 11: 6 sta. 138 ( 1); 11: 7 sta. 268 ( 1);
11: 9 sta. 129 (1, TYPE); 11: 10 sta. 394 (fgm); 11:12 sta. 127 ( 1);
12:21 sta. 412 (24); 13:18 sta. 544 ( 4); 13:20 sta. 480 ( 1); 18:lb sta. 941 ( 1).
Description: This is a small form; length of body about 25 mm, width 3 mm, and segments number 34. Another, from sta. 250, measures 9 mm long by 2.6 mm wide and consists of 28 segments. The prostomium is quadrate, slightly longer than wide (Fig. A), and lacks eyes. The two pairs of antennae are subequal and inserted frontally. A pair of large nuchal organs is located at the postectal margins. The dissected proboscis terminates distally in 21 or 22 rows of terminal and subterminal papillae. Parapodia are widely biramous, with acicular lobes conspicuously conical and projecting.
Interramal cirri are involute and first present at segment 12, or their origin varies; in one (sta. 480), they occur from segment 9; in 3 samples (sta. 129, 412 and 544) they occur from segment 11; in one lot (sta. 250) from 12, in another (sta. 268) from segment 13, and in two lots (sta. 260 and 691) not before segment 16.
Parapodia are best characterized by the long, conical acicular lobes in notopodia and neuropodia, and the short, broadly rounded postsetal lobes. The superior lobe over notopodia is erect in anterior segments (Fig. B). The interramal cirrus surpasses the notopodial lobe within a few segments after its first appearance; it is smooth or transversely wrinkled. Preacicular setae (Fig. C) are transversely barred and much shorter than the nearly smooth postacicular setae; these vary from broader (Fig. D), in the middle part of the fascicle, to much slenderer (Fig. E), in the ends of the series. Furcate setae have not been identified.
A. posterobranchus is separable from other species of the genus by its posterior origin of interramal cirri, its long, conical acicular lobes, and its origin from abyssal depths of Antarctic seas.
Distribution: Off Chile, in 3655-3651 m; South Georgia, in 30563118 m; Drake Passage, in 3678-3803 m; South Shetland Islands, in 2763-4758 m; Bransfield Strait, in 1180 m; South Orkney Islands, in 2800 m; Pacific Antarctic Basin, pelagic in 2562 m over 4118 m."
(Hartman, 1967)
