Argopecten sverdrupi (Durham, 1950)
DURHAM, J. W. 1950. Megascopic paleontology and marine stratigraphy. In: 1940 E. W. Scripps Cruise to the Gulf of California, pt. II: Geological Societyof America Memoir 43: 1-216, pls. 1-48. [p. 64, pl. 8, figs. 2, 5; pl. 9, fig. 7].
1950 Aequipecten sverdrupi Durham, 1950
J. W Durham, 1950, plate 9.
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«Shell of medium size, fairly heavy, resembling A. impostor (Hanna) but having only 17 or 18 heavy rounded ribs; obliqueness of valves varying considerably, some specimens being markedly oblique to posterior; ribs rounded, interspaces about half as wide; in one small specimen the younger half of shell, after a heavy constriction representing a marked pause in growth, shows very high ribs on right valve with relatively narrow interspaces, while on left valve the ribs are high but with wide interspaces; anterior ears missing from all six valves at hand; however, the traces of byssal notch present indicate that it was deep and fairly sharply angled, like that of A. circularis.
Holotype no. 15995, paratypes nos. 15996, 15997, 15998 (all from loc. A 3583).
OCCURRENCE: locs. A 3576, A 3583, loc. 740 (Imperial formation). RANGE: lower Pliocene. REMARKS: The 17-18 heavy rounded ribs appear to be characteristic of this species». JOHN WYATT DURHAM, 1950
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