Euvola catianus (Weisbord, 1964)
WEISBORD, N. E. 1964. Late Cenozoic Pelecypods from Northern Venezuela. Bulletins of American Paleontology, 45 (204): 1-564, pls. 1-59. [p. 119, pl. 11, figs. 9-13]
1964 Pecten (Pecten) catianus Weisbord, 1964
N. E. Weisbord, 1964, plate 11.
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«Shell of medium size, thin, a trifle wider than high, inequivalve, nearly equilateral. Right valve moderately convex, the left valve concave, the beak of the right valve flattish, the point extending slightly beyond the hinge line. Hinge line straightish, the ventral margin of the disk well rounded, the dorsal margins slightly concave, diverging at an angle of about 94 degrees. Auricles of right valve a little unequal, the posterior ear triangular, sharply truncate at the margin which is oriented vertically or parallel with the beak-to-base axis, the anterior ear subrectangular, its margin subtruncate, gently scalloped at the edge and also parallel with the beak-to-base axis, the base of the anterior ear with a moderately prominent notch at the byssal area. Both ears are marked on the lower part by four feeble low radial folds or riblets, but on the upper part radial markings are absent; the shallow fasciolar depression between the disk margin and lowest rib of the anterior ear is somewhat wider than the corresponding shallow groove of the posterior ear; the exterior of both ears on the right valve is traversed by numerous inconspicuous concentric lineations. Internally, the right anterior ear is weakly fluted distally, the flutings corresponding with the external riblets. The auricles of the left valve are sunken below the exterior submargins, are sculptured by two, and possibly three radial riblets, and are traversed by sharp closely spaced concentric lamellae. Interior of right valve with a deep triangular chondrophore and a cardinal crura running along the inner margin of either ear, the posterior crura a little thicker at the distal end than the anterior. A feeble arcuate cardinal ridge is present on the posterior ear, the ridge merging with the ligamental groove a short distance in from the end. Along the ventral margin of the right valve there are 21 radial bicrenulate ribs, these internal ribs separated at the base by deep elongate triangular flutings, the flutings becoming narrow shallow interspaces upward, the ribs and interspaces dying out toward the body cavity. The exterior of the right valve is sculptured by 22 radial ribs, and is crossed by strong regularly spaced concentric ridgelets. The radial ribs are squarish but gently rounded at the crest, and are separated by somewhat narrower interspaces with evenly rounded bottoms. The radial rib at either margin of the disk is rendered bipartite by a faint longitudinal groove. The concentric ridgelets are strong and rounded, and pass over the top of the ribs where they are often eroded away but where normally they are nearly as pronounced -as in the interspaces; on the submargins, however, the concentric cords disappear. The character of the inner surface of the left valve is not known. The exterior of the left valve is sculptured by 20 or 21 radial ribs with slightly narrower interspaces, and by closely packed concentric cords which cross both the ribs and intercostal areas in equal strength; the concentric cords are rounded but corrode into lamellae or foliations; on the shouldered submargins of the left valve the concentric cords or lamellae become obsolescent and appear as inconspicuous lineations.
Dimensions.— Holotype (K330a), both valves attached, height 36.2 mm.; width 36.9 mm. Paratype (K332a), right valve, height 23.3 mm.; width 33.6 mm.; thickness 7.6 mm. Type locality.—Playa Grande formation (Catia member), in bluff 125 meters west of the intersection of the Playa Grande Yachting Club road and coast road. Three specimens including one doublet (holotype), one right valve (paratype), and one fragment of a right valve. Remarks.— The distinguishing character of this species, though not brought out well on the illustration, is the unusually coarse concentric cording. These cords are continuous over the disk and are as pronounced on the ribs as in the intercostal spaces on unweathered examples. Comparisons.— The new species is allied to Janira soror Gabb (1873, Amer. Philos. Soc, Trans., new sen, vol. 15, p. 257) (see Pilsbry, 1921, Acad. Nat. Sci. Philadelphia, Proc, vol. 73, p. 410, pl. 44, figs. 1-2) from the middle Miocene of the Dominican Republic; to P. barretti Woodring (1925, Carnegie Inst. Washington, Publ. No. 366, pp. 62-63, pl. 7, figs. 6-7) from the middle Miocene of Jamaica; to P. soror urumaconis Harris (1927, Bull. Amer. Paleont., vol. 13, No. 49, pp. 22-23, pl. 13, fig. 1; pl. 14, figs. 3-4) from the Miocene of the State of Falcon, Venezuela; and to P. ventonensis Cooke (1919, Carnegie Inst. Washington, Publ. No. 261, pp. 130-131, pl. 12, figs, 1a, b) from Cuba, in what is stated to be the Oligocene. On the left valve, the radial ribs of P. soror are narrower and the interspaces much wider than on P. catianus, n. sp., and the concentric markings, though crossing both the ribs and interspaces as they do on the Cabo Blanco left valve, are lamellar rather than cordlike. On the right valve, the auricular riblets of P. barretti are smaller, stronger, and more numerous than on P. catianus, n. sp., and the concentric markings are lamellar instead of cordlike, P. soror urumaconis is a closely related form, but the ears of the left valve are bent decidedly inward, and the one or two radial riblets are nearer the hinge line than on the Cabo Blanco shell; also, the right valve of P. soror urumaconis is much more gibbous than that of P. catianus. On the Cuban P. ventonensis, the byssal notch of the right valve is shallower than on P. catianus, and the concentric markings on the disk are much finer.» NORMAN EDWARD WEISBORD, 1964
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