Parvamussium retiaculum 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. 28, Figs. 35-38]
1995 Parvamussium retiaculum Dijkstra, 1995
H. H. Dijkstra, 1995, figures 31-38.
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«TYPE MATERIAL. — Holotype MNHN. Paratypes: 25 MNHN, 2 AMS C201712, 2 HD, 2 NMNZ M268536, 2 NSMT, 2 USNM.
TYPE LOCALITY. — Southern New Caledonia, BIOCAL, stn DW 51, 23°05' S, 167°45' E, 680700 m.
MATERIAL EXAMINED. — New Caledonia. BIOCAL: stn DW 33, 23°10' S, 167°10' E, 675-680 m, 2 Iv (paratypes). — Stn DW 36, 23°09' S, 16Tll' E, 650-680 m, 2 Iv (paratypes). — Stn DW 48, 23°00' S, 167°29' E, 775 m, 2 Iv (paratypes). - Stn DW 51, 23°05' S, 167°45' E, 680-700 m, 7 spms, 8 lv, 15 rv (holotype and paratypes: 2 AMS, 2 HD, 19 MNHN, 2 NMNZ, 2 NSMT, 2 USNM).
DISTRIBUTION. — Southern New Caledonia 650-775 m, living 680-700 m.
DESCRIPTION. — Shell small, fragile, suborbicular, inequivalve, up to ca. 7 mm high, left valve slightly more convex than right, semi-transparent white, auricles of unequal size, umbonal angle about 100°
Prodissoconch ca. 210 Ilm in height. Left valve sculptured with 14 prominent, widely spaced, concentric lamellae, starting weakly at ca. 2 mm shell height, extending to ventral margin. Delicate, regularly spaced radial riblets, commence at about 3 mm shell height, and extend to ventral margin. Exterior of disc with semi-reticulated sculpture produced by concentric lamellae and intersecting radial riblets. Anterior auricle stronger than posterior sculptured with close-set, irregularly spaced concentric lamellae; posterior auricle with identical though weaker sculpture. Hinge line straight. Right valve with regularly spaced concentric lirae, close-set near umbonal area and becoming more widely spaced toward ventral margin. Anterior auricle more strongly sculptured near lateral margin with concentric lamellae. Hinge line somewhat elevated due to strong concentric lamellae. Byssal fasciole present. Each valve with 12 internal lirae and I auricular lira that commence rather late and extend to near the periphery; one rudimentary interstitial lira on left valve near the ventral margin. Outer ligament well developed and rather broad on posterior auricle. Small byssal notch, no ctenolium. Dimensions of the holotype: H 7.3, L 7.2, D 1.9 mm. REMARKS. — P. retiaculum is somewhat similar to P. multiliratum, although the latter is slightly larger and more orbicular, while the auricles are more equal and smaller, fewer radial riblets are developed on the left valve, there are more internal lirae, and the hinge line of the right valve is straight. P. multiliratum lives at much great depths (lower bathyal to upper abyssal).
The right valve of P. torresi is somewhat similar to that in P. retiaculum, although the internal lirae commence earlier, and are fewer in number (generally 10). Moreover, the left valve of P. torresi is glossy and nearly smooth, whereas P. retiaculum is prominently sculptured and dull. The left valve of P. thetidis is covered with prominent irregularly spaced, radial costae and delicate close-set concentric lamellae, whereas P. retiaculum has prominent concentric lamellae, and delicate radial riblets. ETYMOLOGY. — From the cancellate sculpture of the left valve (Lat. retiaculum, n. net, lattice-work, wattle-work).»
HENK H. DIJKSTRA, 1995
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