Cyclochlamys irregularis 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. 28, figs. 25A-25E]
2008 Cyclochlamys irregularis Dijkstra & Marshall, 2008
H. H. Dijkstra & B. A. Marshall, 2008, figure 25.
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«Type material
Holotype (l v) NMNZ M.183889, and paratypes (50 v, M.155423; 3 v, ZMA Moll. 4.07.003); off Whangaroa Bay, 34º54.0’S, 173º42.6’E, 83 m, 26 Jan. 1981, RV Tangaroa. Material examined
The type material (see above). Off Three Kings Islands: Middlesex Bank, 33°59.9’S, 171°45.3’E, 186–196 m (3 v, M.112824); Three Kings Trough, 34°00’S, 171°55’E, 805 m (1 v, M.155884); 34°01’S, 172°07’E, 622 m (l v, M.34984); Middlesex Bank, 34°02.0’S, 171°44.0’E, 246–291 m (l v, M.107600); 34°02.1’S, 171°45.8’E, alive, 221–206 m (1 pr, M.155886); submarine cave, S side of Rosemary Rock, Princes Islands, 34º10.5’S, 172º04.0’E, 20 m (10 v, M.117157); Arch Pinnacle, Princes Islands, 34°10.5’S, 172°03.0’E, 44 m (2 v, M.155419); Arch Pinnacle, 34°10.5’S, 172°03.0’E, 38 m (1 v, M.155420); off N face of Hinemoa Island, 34°10.8’S, 172°02.6’E, 23 m (1 v, M.155415). Matai Bay reef, Karikari Peninsula, 34°50’E, 173°25’S, 42 m (2 v, M.155416). Off Cavalli Islands, 91 m (1 v, M.111944). Poor Knights Islands: (5 v, M.112225; Middle Arch, Tawhiti Rahi, 35º28’S, 174º44’E, 30 m (2 v, M.119444); Northern Arch, TeAraara Point, 35°27’S, 174°44’E, 50 m (3 v, M.155421); South Harbour, Aorangi Island, 35º29’S, 174º44.5’E, 25 m (2 v, M.155422); Riko Riko Cave, Aorangi Island, 35°29’S, 174°44’E, 30 m (6 v, M.155417); off Ngoio Rock, 35º29.5’S, 174º44.2’E, 30 m (5 v, M.155418); 35°32’S, 174°41’E, 121–113 m (9 v, M.35907). Description
Shell up to 3 mm wide, inequilateral, posteriorly oblique, about as wide as high, translucent white. Outline irregular, variable, and typically changing during ontogeny, commonly associated with change in spacing of commarginal lamellae and direction of radial riblets (habitat constriction). Prodissoconch c. 300 μm long, boundary unclear, but possibly outermost of 2 earliest commarginal ridges following PI, roundly conical; PI c. 150 μm long, D-shaped (i.e. valve margins), swollen, bounded by rounded, flangelike rim with concave dorsal surface, sculptured with 5 rounded radial ridges, median strongest and gently inclined posteriorly; PII weakly convex, sculptured with fine, crisp, irregularly anastomosing radial threads. Dissoconch left valve disc and auricle sculpture commencing immediately, crisp; comprising widely and rather irregularly spaced, high, narrow, commarginal lamellae, traversed by slightly finer radial riblets (c. 12 per mm on central disc) that multiply by intercalation, small rounded nodules at intersections; interspaces more or less as wide as those of the commarginal lamellae, widest over centre of disc. Posterior auricle distinctly larger than anterior auricle. Right valve disc and all but dorsal border of posterior auricle with outer layer of commarginally elongate, hexagonal prisms. Anterior auricle with low commarginal ridges and up to 6 radial threads that multiply by intercalation, intersections finely nodular. Byssal notch of moderate depth, byssal fasciole rather broad. Distribution
Off Three Kings Islands and NE North Island, New Zealand, 20–622 m (shells only) (Fig. 24) Remarks
Cyclochlamys irregularis differs from the superficially similar species Cc. aupouria, Cc. delli and Cc. wanganellica in having more widely spaced radial riblets that form small nodules where crossing the commarginal lamellae, and in prodissoconch sculpture. Cyclochlamys irregularis is also somewhat similar to Cc. transenna (allopatric), but differs principally in being less oblique, and in having finer nodules at the intersections of the primary sculptural elements on the left valve. A somewhat similar species from Fiordland and the Antipodes Islands is Cc. austrina n. sp., described above. Although paired individuals of Cc. irregularis are unknown, there seems little doubt that dissociated right and left valves at the type locality are conspecific because left valves of no other Cyclochlamys (or Cyclopecten) species occurred with them. Etymology
Irregular (Latin), alluding to the shape variation within and between specimens.» HENK H. DIJKSTRA & BRUCE A. MARSHALL, 2008
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