Cyclopecten exquisitus Grau, 1959
GRAU, G. 1959. Pectinidae of the eastern Pacific. Allan Hancock Pacific Expeditions, 23: viii, 308 p., pls. 1-57. University of Southern California Press. Los Angeles, California. [p. 34, pl. 12]
1959 Cyclopecten exquisitus Grau, 1959
G. Grau, 1959, plate 12.
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«Shell very small, largest valve found measuring 6 mm in height and length; rather thin but opaque, inequivalve and inequilateral; beaks closer to posterior margin and protruding a little above; hinge line nearly as long as disk. Right valve of low convexity and slightly smaller than left; very numerous minute radial ridges crossed by more prominent concentric lamellae which are higher over radial ridges, resulting in scalloped effect; anterior auricle longer than posterior, with 10 to 12 rather faint radial ridges and 20 to 25 rows of more prominent concentric lamellae, the latter produced above hinge margin and appearing in profile as spines; byssal notch moderately deep and no ctenolium; posterior auricle slightly produced, with shallow sinus below, and having 6 major riblets nearest hinge margin, several minor ones adjoining disk, and 8 to 12 rows of concentric lamellae. Left valve moderately convex except for posterior ⅓ of disk, which is slightly flat or very shallowly concave; 14 to 19 primary radial ridges, with 1 to 4 smaller intercalary ridges between them, intercalaries beginning at various distances from umbonal area; 22 to 24 rows of concentric lamellae, much more prominent than those on right valve and, as on that valve, higher over radial ridges, with resultant scalloped effect; anterior auride moderately produced, with well-defined sinus below; 8 to 10 low radial ridges and 8 rows of fairly prominent concentric lamellae; posterior auricle slightly produced, with shallow sinus below; 8 low radial ridges and 8 rows of concentric lamellae. Interior of each valve flattened near ventral margin. Both valves white or yelIow-white; left valve often with streaks or patches of yellow, brown or red-brown, less frequently red or red-orange.
On the holotype part of the posterior auricle of each valve is broken off, giving the impression that no posterior sinus exists; a number of single valves in perfect condition were found, and they show the actual length of the auricles. Holotype: Height and length 3.5 mm; diameter 1 mm; hinge line 3 mm. Allan Hancock Foundation. Type locality: Off Wenman Island, Galapagos Islands, in 100-150 fathoms, coral and nullipores; Hancock station 143-34; 1° 23' 10" N, 91°48' 45 W; January 11,1934. Geographical range: Galapagos Islands; Callao, Peru, to Angel de la Guarda Island, northern Gulf of California. Geochronological range: Recent only. Bathymetric range: 12 to at least 150 fathoms. Ecological data: Usually found on sand bottoms, occasionally rock; associated with coral, coralline and nullipores. Remarks: This beautiful little species is quite distinct from any other eastern Pacific Cyclopecten. As it occurred at 45 Hancock stations and is so widely distributed, it seems remarkable that it remained so long undiscovered. While this paper was in press Dr. Harald A. Rehder sent the author some additional lots of unidentified material from the U. S. National Museum. One lot comprised a number of single valves of C. exquisitus taken April 7, 1888, at Albatross station 2813, off Hood Island, Galapagos Islands, in 40 fathoms; Dall labelled the specimens "Pseudamussium sp." Hancock Expeditions Collecting Stations:
GALAPAGOS ISLANDS: Albemarle, Barrington, Charles, Duncan, Gardner, Hood, lames, and South Seymour Islands; 22 stations, 12-150 fathoms, sand. PERU: Callao; 210 fathoms, bottom sample 552 (dead). COLOMBIA: 8 stations; Gorgona Island to Octavia Bay; 32-75 fathoms. PANAMA: Bahia Honda; 30-50 fathoms, bottom sample 332. COCOS ISLAND, COSTA RICA: Chatham Bay; 30-50 fathoms, bottom sample 329. GULF OF CALIFORNIA: 12 stations; Outer Corda Bank, north to Angel de la Guarda Island; 40-95 fathoms, rock, sand.» GILBERT GRAU, 1959
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