Amussiopecten antiguensis (Brown, 1913)
BROWN, A. P. 1913. Notes on the geology of the island of Antigua. Proceedings of the Academy of Natural Sciences of Philadelphia, 65: 584-616. [p. 613, pl. 18, figs. 1-3, 5]
A. P. Brown, 1913, plate 18.
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«Inequivalve, shell orbicular, rather thin, convex; the surface covered with a fine concentric sculpture, following the growth lines; with about 13 radial ribs running from the beaks, where they are very pronounced, and, in one valve, apparently disappearing towards the margin, but in the other valve continued as undulations of the shell to the margin. The interior of the shell has radial ribs extending to the margin, where the adjacent pairs of ribs contract and are then seen to be paired, but otherwise seeming to be equally spread as in P. (Amusium) lyonii Gabb, from which this species differs in having a strong concentric sculpture (wanting in P. lyonii), and also in the external radial ribbing being continued for a greater distance from the beak than in Gabb's species. The species is likewise related to P. sol B, and P., but this latter has shorter radial external ribs and the internal ribs are paired. The ears are separated from the rest of the valve by a depression, as is the case in P. sol. Length and height about equal — 70-75 mm.
Hodge's Bay and Wetherill's Bay in the Antigua limestone, with Orbitoides, etc., Oligocene. Cotypes A. N. S. P. Collection, invertebrate fossils, No. 1,648.» AMOS PEASLEE BROWN, 1913
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«Of medium size, height little less than length. Right valve slightly convex, left valve barely convex. Auricles not ribbed, depressed; byssal notch shallow. Right valve sculptured with 18 to 21 ribs; moderately strong for distance of 5 to 10 mm from umbo, greatly subdued on remainder of valve; slightly wider than interribs, or of about same width. Left valve sculptured with 17 or 18 ribs; greatly subdued throughout, or moderately strong in umbonal area to distance of 15 rom; narrower than interribs; or of about same width. Fine, closely spaced concentric lamellae visible on some valves. On right valve, interior paired lirae extending from ventral margin upward for variable distance, as much as two-thirds of distance to umbonal area; lirae showing through to exterior on some valves. On left valve, interior lirae about equidistant, also extending upward for variable distance, as much as two-thirds of distance to umbonal area. A pair of strong dorsal cardinal crura, two other weak pairs, and a pair of elongate auricular crura.
Length (incomplete) 60 mm (estimated restored length 80 mm), height 74 mm (left valve figured in interior view, largest specimen). Length (practically complete) 54 mm, height 50 mm, convexity (both valves) 11 rom (figured articulated specimen). Type material: Lectotype, herewith designated, the valve illustrated in Brown's figure 1, Acad. Nat. Sci. Philadelphia 1648. Type locality: Hodge's Bay, Antigua, Antigua formation. A species of Flabellipecten, identified as F. antiguensis, like F. gatunensis protistus, in the Canal Zone has an age range from late Oliogene to the early part of early Miocene. Not only is the largest number from the La Boca proper, but the best preservation also is found in that unit.
The type material of F. antiguensis is in poor condition, and the number of ribs is indeterminable. On the largest available topotype (the left valve shown in Cooke's figure 7 and Masuda's figure 5; USGS locality 6862, USNM catalog no. 167139) 18 ribs can be counted in the umbonal area, and about 17 on the small right topotype illustrated in Masuda's figure 4 (USGS 9200b, same locality as 6862, but a different collection and collector; the valve now cataloged as 646993). Despite the deficiencies in the Antiguan specimens, they show the basic features of F. woodringi, which was based on well-preserved articulated Puerto Rican specimens. Though the fossils from the Caimito formation are disfigured by a partial coating of intractable matrix, the right valves show the characteristic ribbing. The Bohio fossils are in better condition, but are incomplete. The collection from La Boca locality 99f includes several partly exposed valves in addition to those tabulated, and others doubtless would appear if the massive calcareous sandstone could be split. The largest, the interior of a left valve, is illustrated on plate 96, figure 3. An articulated specimen is of medium size (pl. 96, figs. 1, 2). The specimen from the Emperador limestone member of the La Boca in Madden basin is articulated and very small (height 33 mm). Occurrence: Bohio formation (late Oligocene), locality 42d. Caimito formation (late Oligocene), localities 56, 57. La Boca formation (early Miocene), Gaillard Cut area, localities 99f, 119c. Emperador limestone member of La Boca formation (early Miocene), Gaillard Cut area, locality 117b; Madden basin, locality 71. Antigua formation (late Oligocene), Antigua. Lares limestone (late Oligocene), Puerto Rico.» WOODRING, W. P. 1982. Geology and paleontology of Canal Zone and adjoining parts of Panama. United States Geological Survey Professional Paper, 306-F: 1-759, pls. 83-124. [p. 586]
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Flabellipecten antiguensis (Brown); W. P. Woodring, 1982, Geology and paleontology of Canal Zone, plate 96, figures 1-3.
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