Argopecten borinquenensis (Hubbard, 1920)
HUBBARD, B. 1920. Tertiary Mollusca from the Lares District. New York Academy of Sciences Survey of Porto Rico and the Virgin Islands, 3 (2): 79-164. [p. 95, pl. 14, figs. 1, 2]
1920 Pecten (Plagioctenium) borinquenensis Hubbard, 1920
B. Hubbard, 1920, plate 14.
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«Shell sub-orbicular, sub-equivalve, slightly oblique, sub-marginal slopes slightly concave (left valve slightly less); sculpture of the two valves dissimilar. Right valve with sixteen to nineteen strong flat ribs of T-rail crosssection, wider than interspaces, especially in the unworn specimens where the lateral overhang obscures the borders of the interspaces; interspaces rounded and sculptured with raised concentric threads, very regular and evenly spaced (one-fifth mm. apart in ventral part of shell); tops of ribs marked by obscure median keel; concentric threads cross the ribs and are bowed up in the form of lamellae on crossing the median keel. The ribs are usually worn smooth showing the lamellae on top as a series of V-shaped striations; ears sub-equal, small; hinge line less than half the length of shell, sub-margins nearly smooth; ctenollum obscure and marked by deep byssal groove bordering the line of teeth; byssal notch small; adductor scar large, central; left valve with seventeen to twenty-one strong, high, rounded ribs and sub-equal rounded interspaces; both ribs and interspaces crossed by fine raised concentric threads, somewhat irregular and more distantly spaced than in the right valve, and worn or obscure on crossing the ribs; ears sub-equal and sculptured by radial grooves and incremental lines; submargins as in the right valve. Interior of both valves smooth or faintly fluted, but strongly fluted and lirate around the ventral margins; greatest convexity in the umbonal region. The ribs of both valves are rounded in the nepionic stage. Adult shell measures in length 32 mm., height 31 mm., diameter of right valve 10 mm.
This shell has ribs similar to P. diegensis Dall of the Pacific Coast Pleistocene, but is otherwise a different shell. Maury's P. caimitica, a single left valve from the Santo Domingo Miocene is similar to the left valve of this shell. Locality.— 313. Horizon.— Upper Quebradillas limestone». BELA HUBBARD, 1920
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«Argopecten borinquenensis (Hubbard, 1920) from the Neogene of Puerto Rico is morphologically intermediate between A. uselmae and the extant species A. noronhensis. The left valve of the Puerto Rican species consistently has keeled ribs, but the ribs of its right valve lack the knife-edged rib crests of A. noronhensis and develop a secondary riblet at the base of each right-valve rib late in ontogeny. Specimens of A. borinquenensis in the Smithsonian's collections are from USGS 17952, a mile east of the Arecibo lighthouse. This locality was mentioned by Monroe (1980: 63), who assigned it to the upper member of the Camuy Formation, of probable
Pliocene age.» WALLER, T. R. 2011. Neogene Paleontology of the Northern Dominican Republic. 24. Propeamussiidae and Pectinidae (Mollusca: Bivalvia: Pectinoidea) of the Cibao Valley. Bulletins of American Paleontology, 381: 1-197, pls. 1-18. [p. 66]
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