Comprehensive DescriptionRead full entry
“Asthelys antarctica n. sp.
Description. Shell up to 5.80 mm in diameter, about as broad as high, inequibiconical, umbilicate, spire about 1.7× (est.) higher than aperture; brilliant nacreous pink and blue beneath thin, translucent outer shell layer. Protoconch and most of 1st teleoconch whorl missing. First two remaining teleoconch whorls (i.e., 2nd and 3rd whorls) shallowly convex, thereafter very shallowly convex, periphery sharply angulated, base shallowly convex. After 1st remaining teleoconch whorl (2nd) a suprasutural spiral appears and gradually enlarges to become a rounded peripheral spiral cord, this splitting at end of 3rd remaining whorl (4th) to form two similar, closely-spaced, peripheral spiral cords, with abapical side of abapical spiral covered by succeeding whorls. A weaker spiral cord on base immediately below periphery. Another subsutural spiral cord arises on the last half of the body whorl in the larger paratype. First remaining whorl finely and crisply granulate throughout, subsequent spire whorls and base finely and closely pitted, most pits arranged in spiral lines. Fine collabral growth lines throughout, more prominent on 1st few whorls. Umbilicus deep, diameter 14.9-20.7% of shell diameter, rim with a
rounded spiral cord, wall very finely spirally lirate. Aperture rhomboidal, lips thin and simple. Posterior and basal notches broad and shallow, posterior notch very shallow.
Animal. Head broad, snout longer than broad and indented in front, oral shield broad. Cephalic tentacles dorsoventrally flattened, the left larger, finely ciliated, gradually tapered to pointed tips. A prominent egg-shaped eye at outer base of each cephalic tentacle, posterior wall darkly pigmented, otherwise clear and colourless. Penis (?-groove not detected) about as large as cephalic tentacle, emerging from base of right eye. Epipodial tentacles numbering 7 on right side and 4 on left, the latter larger. A tight cluster of about 10 fine tentacles in front of base of left cephalic tentacle. There is no accessory cephalic process. Operculum typical of the family.
Radula (Fig. 4A-C) cross-row formula c. 20 + 1 + 1 + 1 + c. 20. Central tooth subrectangular, longer than broad, cutting area tapered, finely and sharply serrated, suddenly and broadly expanded laterally at base to form a seat for lateral teeth. Laterals subtriangular, cutting area narrowly tapered, edges finely and sharply serrated. Marginals slender. Innermost marginal stout, with a strong terminal cusp, outer edge of shaft finely and sharply serrated for about half its length distally. Inner marginals narrower, narrowing outwards, tips tapered, with fine, long, narrow cusps on both edges, outer edge of shaft finely and sharply serrated along about a third its length distally.
Type data. Holotype USNM 859074, and one paratype (NMNZ): Eltanin stn 135, 62°40'S, 64°06’W, Southern Antilles Basin, off South Shetland Islands, Graham Land, Antarctica, alive, 3715-3752 m, 6 Aug 1962.
Remarks. Asthelys antarctica differs from both A. simplex and A. munda in having more closely spaced peripheral spiral cords and in lacking spiral cords between the subperipheral spiral and the umbilical rim. It differs further from A. simplex in having a more broadly conical spire and a shallower posterior notch; and from A. munda in having a smooth spiral cord instead of axial pleats at the umbilical rim, and a broader umbilicus.”
(Marshall, 1988: 237)