Cyclochlamys wanganellica Dijkstra & Marshall, 2008
DIJKSTRA, H. H. & B. A. MARSHALL. 2008. The recent Pectinoidea of the New Zealand region (Mollusca: Bivalvia: Propeamusiidae,Pectinidae and Spondylidae). Molluscan Research, 28 (1): 1-88, figs. 1-70. [p. 37, figs. 29F, 29J]
2008 Cyclochlamys wanganellica Dijkstra & Marshall, 2008
H. H. Dijkstra & B. A. Marshall, 2008, figure 29.
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«Type material
Holotype NMNZ M.158254 and 3 paratypes (2 pr, 1 v) M.107601; Wanganella Bank summit, West Norfolk Ridge, 32°34.4’S, 167°31.0’E, alive, 113 m, 29 Jan. 1981, RV Tangaroa. Paratypes: Wanganella Bank summit: 32°31.8’S, 167°29.5’E, alive, 113–118 m (2 pr, M.257182); 32°32.2’S, 167°30.7’E, alive, 113 m (3 pr, M.257273; 1 pr, ZMA Moll. 4.07.004); 32°32.6’S, 167°29.2’E, alive, 133 m (1 pr, M.107598). Material examined
The type material (see above). Description
Shell up to 2.55 mm wide, slightly wider than high, subcircular, equivalve (broad, thin ventral margin of right valve disintegrating post mortem: thickened inner part 84–85% height of left valve), left valve more convex than right valve, umbonal area opaque white, few irregular, opaque white radial streaks on both valves, elsewhere colourless and translucent. Hinge line straight. Prodissoconch 270 μm long (brooded), sharply bounded by commarginal lamella; PI c. 130 μm long, Dshaped (i.e. valve margins), weakly wrinkled, bounded by rounded rim, projecting tip roundly coeloconoid; PII convex, sculptured with crisp radial threads that are continuous with those of adjacent dissoconch. Left valve disc and auricle sculpture commencing immediately, crisp; comprising widely and rather regularly spaced, high, thin commarginal lamellae, and much finer, more closely spaced radial threads (c. 24 per mm on central disc). Posterior auricle slightly larger than anterior one. Right valve disc and all but dorsal border of posterior auricle with outer layer of commarginally elongate, hexagonal prisms that form broad, flexible ventral apron. Posterior auricle with low commarginal lamellae and 1 or 2 finer radial threads beside dorsal margin. Anterior auricle with low commarginal lamellae and 4 or 5 radial threads. Byssal notch of moderate depth, byssal fasciole rather broad. Distribution
Wanganella Bank summit, West Norfolk Ridge, taken alive at 113–133 m from rhodolith gravel (Fig. 30). Remarks
Among species with similar dissoconch facies, Cyclochlamys wanganellica is distinctive in having a colourless, translucent shell with opaque white streaks. It differs further from Cc. aupouria, which has similar prodissoconch morphology, in that prodissoconch II has one rather than two commarginal lamellae, in attaining smaller size (width up to 2.55 mm versus 4.00 mm), and in having closer commarginal lamellae and finer radial sculpture on the dissoconch. Etymology
After the type locality, Wanganella Bank.» HENK H. DIJKSTRA & BRUCE A. MARSHALL, 2008
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