Figure 30
Material Examined. Ross Sea, off Cape Adare, USNS Eltanin Cr. 27, Sta. 1869, 13 Jan 1967, 71.267°S, 171.667°E, trawl, 1565–1674 m, holotype ( USNM 60691).
Description. Holotype small, complete, 4 mm long and 0.3 mm wide for 17 setigerous segments. Anterior end narrow, middle body segments inflated, tapering posteriorly to narrow pygidium ( Fig. 30E). Oocytes present in posterior segments. Color in alcohol: light brown.
Prostomium large, bluntly conical; eyespots lacking; nuchal organs not observed ( Fig. 30A). Peristomium with two achaetous rings, incomplete dorsally; dorsal tentacles inserted in groove between peristomium and anterior edge of setiger 1 ( Fig. 30A). A single pair of short branchiae lateral to dorsal tentacles on posterior margin of peristomium ( Fig. 30A); segmental branchiae, scars, or stubs not observed.
Parapodia reduced, lacking parapodial lobes. Setiger 1 with two setae in noto- and neuropodia: one a simple capillary, the other a narrow curved spine; heavy acicular spines ( Fig. 30 B–C), numbering 3–4 per fascicle present from setiger 2, these sometimes accompanied by 1–2 narrow spines having a fimbriated edge ( Fig. 30D), and a single long capillary seta. Pygidium a simple flattened lobe ( Fig. 30E).
Etymology. The epithet is from the Latin, abyss for deep sea.
Remarks. Chaetocirratulus abyssalis n. sp. has acicular spines from setiger 1 in both noto- and neuropodia. In this respect the species approaches C. pinguis, but otherwise differs in body shape and by having up to four spines per neuropodium instead of 1–2.
Distribution. Ross Sea, Antarctica, 1565–1674 m.