Cyclopecten horridus 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. 41, figs. 63-64, 98]
1995 Cyclopecten horridus Dijkstra, 1995
H. H. Dijkstra, 1995, figures 63-70, 93-98.
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«TYPE MATERIAL. — Holotype MNHN. Paratypes: 5 MNHN, 2 HD.
TYPE LOCALITY. — Loyalty Islands, MUSORSTOM 6, stn DW 420, 20°29'S, 166°43'E, 600 m.
MATERIAL EXAMINED. — New Caledonia. BIOCAL: stn KG 06, 20°34' S, 166°52' E, 735 m, 1 lv (paratype). — Stn DW 08, 20°34', S, 166° 53', E, 435 m, 3 lv, 2 rv (patatypes: 3 MNHN, 2 HD). BIOGEOCAL: stn DW 307, 20°35' S, 166°55' E, 470-480 m, 1 lv (paratype).
Loyalty Islands. MUSORSTOM 6: stn DW 420, 20°29' S, 166°43' E, 600 m, 1 spm (holotype). DISTRIBUTION. — New Caledonia and Loyalty Islands, shells in 435-735 m, living in 600 m.
DESCRIPTION. — Shell small, suborbicular, inequivalve, up to ca. 6 mm high, left valve more convex than right, marginal apron of right valve pressed against margin of interior of left vave, auricles of nearly equal size, umbonal angle ca. 125°, whitish opaque.
Prodisioconch ca. 220 μm in height. Left valve covered with regular concentric lamellae, closely-set in early ontogeny, enlarging towards periphery. Erect hollow spines developing on lamellae- (Fig. 98), which are stronger near the ventral margin (broken off near umbonal area in all specimens seen). Crowded microscopic granules between concentric lamellae, radial scratches added in late ontogeny. Auricles covered with sculpture identical to that on exterior of disc. Right valve with regular concentric lirae, close-set to 2 mm shell height, then transformed into more widely spaced, undulating concentric lamellae with delicate spines near ventral margin. Granulate microsculpture between the concentric lirae and lamellae. Anterior auricle sculptured with 3 radial riblets covered with concentric lamellae. Posterior auricle poorly differentiated from disc, covered with concentric lirae. Hinge line straight. Antero-dorsal margin with scales, squamae weakly developed on postero-dorsal margin. Byssal notch strongly developed. No ctenolium. Dimensions of the holotype: H 5.9, L 6, D 1.6 mm. REMARKS. — A somewhat similar species is Parvamussium araneum Dijkstra, 1991 from the Indonesian Archipelago. This species has a few internal rudimentary lirae, and micro-sculpture on the right valve has radial scratches. Another related species is P. vidalense (Barnard, 1964) from off Zululand, South Africa. The radial sculpture of P. vidalense is somewhat weaker than in P. araneum, with overriding concentric lamellae, while the erect spines are weaker. Moreover, a few more internal rudimentary lirae are present in P. vidalense than in P. araneum, but they are absent in C. horridus.
Some shell features of C. horridus resemble those characteristic of Delectopecten, such as arrangement of erect spines on concentric lamellae, and strongly developed byssal notch. A ctenolium however, is absent, and the sculpture of the right valve is more similar to that in Cyclopecten. ETYMOLOGY. — From the spiny sculpture (Latin horridus, adj. = bristly).»
HENK H. DIJKSTRA, 1995
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