Cyclopecten cancellus 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. 21, figs. 66-70]
1991 Cyclopecten cancellus Dijkstra, 1991
H. H. Dijkstra, 1991, figures 66-70.
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«Material.— Holotype, sta. 4.153 off SW Salayer, 6°22.4'S 120°26.3'E, Van Veen-grab, depth 130-155 m, calcareous sand with some shells and polychaetes, 28.ix.1984 (left valve) (RMNH 56560); Paratypes, sta. 4.153 (8 valves) (RMNH 56561); 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 56562); sta. 4.020 Tukang Besi Islands, Banda Sea, S of Kaledupa reef, 5°57.4'S 123°45.8Έ, Van Veen-grab (2x), depth 255-275 m, coral sand, 9.ix.l984 (1 valve) (RMNH 56563); sta. 4.034 Tukang Besi Islands, Banda Sea, NW of Binongko, 5°52.5'S 123°58.5'E, Van Veengrab, depth 280 m, coarse calcareous sand, 10.ix.1984 (1 valve) (RMNH 56564); 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 (1 valve) (RMNH 56565); 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 (2 valves) (RMNH 56566).
Description.— Shell very small, nearly equilateral, convex, opaque, strongly cancellated; approximately 3 mm in height and length. Anterior and posterior auricles subequal, umbonal angle about 100°. The umbonal region, till 0.5 mm from the umbo, is smooth and ornamented with a few concentric striae and microscopic radial scratches. After that, about ten primary radial costae and concentric costae start, which are strongly developed towards the ventral margin. Nine secondary radial riblets are present between the primary ones near the ventral marginal region. The concentric costae are slightly weaker than the radial riblets. The entire shell-disc has a cancellated sculpture with scaly intersections. The anterior auricle bears two radial costae with strongly developed crossing concentric costae. The posterior auricle gradually passes into the shell disc and has about the same sculpture as the anterior one.
The exterior sculpture is visible on the inside. The hinge line is straight and the cardinal crura is rather broad. The résiliai pit is triangular. No lirae are seen on the interior surface. The ventral margin is somewhat denticulated. The shell is dirty white to creamy, with some white spots on the inside. Dimensions: height 3.5 mm, length 3.9 mm. Etymology.— The exterior surface of the holotype is strongly cancellated. Differentiation.— The most closely related species is Cyclopecten secundus (Finlay, 1926) from off North Cape (New Zealand), which differs by the presence of more primary and secondary radial costae and rudimental radial riblets; it has tubercles on the intersections. This species has the same outline and dimensions as C. cancellus. Finlay (1926:453) placed C. secundus in a new genus Cyclochlamys. Cyclochlamys is considered a junior synonym of Cyclopecten here.» HENK H. DIJKSTRA, 11991
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