Parvamussium carbaseum Dijkstra, 1991
DIJKSTRA, H. H. 1991. A contribution to the knowledge of the pectinacean Mollusca (Bivalvia: Propeamussiidae, Entoliidae, Pectinidae) from the Indonesian Archipelago. Zoologische Verhandelingen, 271: 1-57, figs. 1-91. [p. 9, figs. 11-21]
1991 Parvamussium carbaseum Dijkstra, 1991
1993 Parvamussium crypticum Hayami & Kase, 1993
1993 Parvamussium crypticum Hayami & Kase, 1993
H. H. Dijkstra, 1991, figures 11-21.
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«Material.— Holotype, sta. 4.031 Tukang Besi Islands, Banda Sea, NW of Binongko, 5°54'S 123°58.4'E, Van Veen-grab, depth 390 m, calcareous sand, some shell gravel, 10.ix.1984 (left valve) (RMNH 56534). Paratypes: sta. 4.031 (right valve, additional description)(RMNH 56535); sta. 4.031 (12 valves) (RMNH 56536); sta. 4.017 Tukang Besi Islands, Banda Sea, S of Kaledupa reef, 5°57.8'S 123°465'E, Van Veengrab, depth 365 m, fine shell gravel, 9.ix.l984 (1 valve) (RMNH 56537); sta. 4.018 Tukang Besi Islands, Banda Sea, S of Kaledupa reef, 5°57.5'S 123°46.5Έ, Van Veen-grab, depth 465 m, fine shell gravel with forams, 9.ix.1984 (2 valves) (RMNH 56538); sta. 4.019 Tukang Besi Islands, Banda Sea, S of Kaledupa reef, 5°57.5'S 123°46.5'E, Van Veen-grab (2x), depth 285-305 m, shell gravel and foraminifera sand, 9.ix.1984 (1 valve) (RMNH 56539); sta. 4.020 Tukang Besi Islands, Banda Sea, S of Kaledupa reef, 5°57.4'S 123°45.8'E, Van Veen-grab (2x), depth 255-275 m, coral sand, 9.ix.l984 (2 valves) (RMNH 56540); sta. 4.033 Tukang Besi Islands, Banda Sea, NW of Binongko, 5°52.5'S 123°58.5Έ, Van Veengrab (2x), depth 250-290 m, coarse calcareous sand, 10.ix.1984 (6 valves) (RMNH 56541); sta. 4.034 Tukang Besi Islands, Banda Sea, NW of Binongko, 5°52.5'S 123°58.5Έ, Van Veen-grab,depth 280 m, coarse calcareous sand, 10.ix.1984 (14 valves) (RMNH 56542); sta. 4.111 Ν of Sumbawa, Bay of Sanggar, 8°19.3'S 118°15.6Έ, Van Veen-grab, depth 175-185 m, volcanic sand and gravel with many species of small shells, few living animals, 21.ix.1984 (6 valves) (RMNH 56543); sta. 4.135 NE Taka Bone Rate (Tiger Isl.), Ε of Tarupa Kecil, 6°28.5'S 121°09.3Έ, Van Veen-grab, depth 495 m, muddy, yellow, calcareous sand with Polychaeta, 25.ix.1984 (2 valves) (RMNH 56544); sta. 4.136 NE Taka Bone Rate (Tiger Isl.), NE of Tarupa Kecil, 6°28.3'S 121°09'E, Van Veen-grab, depth 375 m, muddy calcareous sand with some coral stones, scarce macrofauna, 25.ix.1984 (2 valves) (RMNH 56545); sta. 4.153 off SW Salayer, 6°22.4'S 120°26.3Έ, Van Veen-grab, depth 130-155 m, calcareous sand with some shells and polychaetes, 28.ix.1984 (15 valves) (RMNH 56546);sta. 4.154 off SW Salayer, 6°22.4'S 120°26.2'E, Van Veen-grab, depth 175 m, muddy calcareous sand, with some fine shell gravel, 28.ix.1984 (6 valves) (RMNH 56547); sta. 4.155 off SW Salayer, 6°22.3'S 120°26'E, Van Veen-grab (4x), depth 233-274 m, muddy, fine, calcareous sand with sponges, ophiurids and polychaetes, 28.ix.1984 (1 valve) (RMNH 56548); sta. 4.166 SW Salayer, NE of Pulau Bahuluang, 6°26.2'S 120°26.5Έ, VanVeengrab, depth 300 m, calcareous sand with Foraminifera and some calcareous gravel, 30.ix.1984 (1 valve) (RMNH 56570).
Description.— Shell small, circular and convex, approximately 4 mm in height and length. Anterior and posterior auricles unequal, umbonal angle about 100°. After the dissoconch stage, about ten weak concentric lamellae are seen, with microscopic interstitial scratches. Irregular radial costae start 1 mm beneath the umbo, increasing to a number of about 25 at the ventral margin, with some intermediate small radial costae. The radial costae are provided with small tubercles. Many close set fine concentric lines run over the entire shell-disc. The anterior auricle bears about 14 strongly developed concentric lamellae, which are also present on the posterior auricle.
The interior surface has 17 lirae, with some rudimental interstitial lirae, which nearly reach the periphery. The hinge line is straight and the cardinal crura is rather broad. The shell is milky-white and semi-transparent. Dimensions: height 4.4 mm, length 4.5 mm. Exterior surface of right valve with many small concentric costae. Anterior auricle sculptured with a few weak radial costae. On the hinge line strongly concentric lamellae are present, which are most coarse near the anterior margin. The posterior auricle bears some nodose concentric lamellae. The interior surface has about 13 lirae, with a few additional rudimental interstitial lines. The hinge line is straight and the cardinal crura is rather broad. Small spines are visible on the anterior hinge line; these are very weakly developed on the posterior one. The byssal notch is rather small and there is no ctenolium on the suture. The shell is milky-white and semi-transparent. Dimensions: height and length 4 mm. Etymology.— The surface of the holotype has an appearance of old linen. Differentiation.— Parvamussium cristatellum (Dautzenberg & Bavay) is larger, with more pronounced radial costae and fewer concentric lamellae. Internal lirae are also less in number. P. araneum is larger, with a cancellated structure and has also less internal lirae. P. texturatum has nearly the same number of internal lirae, but differs in external sculpture, which is more prominent with lamellose radiations, instead of the fine nodose radial costae that are typical for P. carbaseum. Remarks.— The number of internal lirae varies between 11 and 17 (generally 11 to 13), with some rudimental interstitial lirae. Sometimes the small nodules on the radial costae of the left valves are absent, whereas the radial costae are not constant in number.» HENK H. DIJKSTRA, 1991
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