Parvamussium multiliratum Dijkstra, 1995
DIJKSTRA, H. H. 1995. Bathyal Pectinoidea (Bivalvia: Propeamussiidae, Entoliidae, Pectinidae) from New Caledonia and adjacent areas. In Bouchet, P. (Ed.), Résultats des Campagnes MUSORSTOM, Volume 14. Mémoires du Muséum national d'Histoire naturelle, 167: 9-73, figs. 1-154. [p. 26, Figs. 31-34, 91-92]
1995 Parvamussium multiliratum Dijkstra, 1995
H. H. Dijkstra, 1995, figures 31-38, 87-92.
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«TYPE MATERIAL. — Holotype MNHN. Paratypes: 11 MNHN, 1 AMS C201711, 1 HD, 1 USNM.
TYPE LOCALITY. — Southern New Caledonia, BIOCAL, stn CP 72, 22°10' S, 167°33' E, 2100-2110 m.
MATERIAL EXAMINED. — New Caledonia. BIOCAL: stn CP 72, 22°10' S, 167°33' E, 2100-2110 m, 2 spm, 1 Iv (holotype and paratypes).
Loyalty Islands. BIOGEOCAL: stn KG 240, 21°29' S, 166°27' E, 1520 m, 1 rv (paratype). - Stn CP 243, 21°28' S, 166°26' E, 1820 m, 1 Iv (paratype). — Stn CP 260,21°00' S, 167°58' E, 1820-1980 m, 2 spms (paratypes). — Stn CP 272, 21°00' S, 166°57' E, 1615-1710 m, 1 spm (paratype). — Stn CP 273, 21 °02' S, 166°57' E, 1920-2040 m, 5 spms (paratypes: 1 HD, 1 AMS, 2 MNHN, 1 USNM). — Stn CP 317, 20°48' S, 166°53' E, 1620-1630 m, 1 lv, 1 rv (paratypes). DISTRIBUTION. — New Caledonia, 1520-2110 m, living in 1615-2110 m.
DESCRIPTION. — Shell rather small, fragile, orbicular, inequivalve, semi-transparent white, up to ca. 9 mm high, left valve slightly more convex than right, auricles subequal, umbonal angle about 110°.
Prodissoconch ca. 220 μm in height. Left valve sculptured with widely spaced concentric lamellae that commence at 3 mm shell height, and extend to ventral margin. Irregularly spaced, delicate radial riblets arising near submarginal region, a few commencing earlier. Umbonal region glossy with some white spots, otherwise transparent and dull due to microscopic granules. Auricles with concentrically lamellate riblets that are closer near lateral margins. Right valve with regularly spaced concentric lirae, somewhat interrupted near submarginal region by a disturbance of growth. Auricles with concentric lamellae that are somewhat stronger on anterior, and more closely spaced on posterior. Hinge line straight, with some scales near margins,that are more prominent on anterior. Byssal fasciole small. Each valve with 14 internallirae plus 2 rudimentary interstitial lirae; one auricular lira on both auricles. External sculpture clearly visible from the interior. Resilifer triangular. Byssal notch present, no ctenolium. Dimensions of the holotype: H 7.9, L 8.9, D 2.4 mm. REMARKS. — The most closely related species is Parvamussium permirum (Dautzenberg, 1925) recorded from the Bay of Biscay (E Atlantic) and adjacent abyssal depths. P. permirum has more regularly spaced radial riblets on the left valve, and fewer concentric lamellae. Internallirae generally 12 with 2-4 additional rudimentary interstitiallirae and the hinge line has fewer scales. P. retiaculum is somewhat similar to P. multiliratum in sculpture, although the latter has fewer radial riblets, and a more strongly orbicular shape, with more numerous internal lirae. DAUTZENBERG (1925: 11) placed P. permirum in Amussium (Variamussium), but all the conchological characters are similar to Parvamussium.
ETYMOLOGY. — So named because the internal lirae are more numerous than usual for a propeamussiid (Lat. liratus, adj. = with lira(e)).»
HENK H. DIJKSTRA, 1995
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