Christinapecten marylandica (Wagner, 1839)
WAGNER, W. 1839. Description of five new fossils, of the Older Pliocene Formation of Maryland and North Carolina. Journal of the Academy of Natural Sciences of Philadelphia, 8 (1): 51-53, pl. 1. [p. 51, pl. 1, fig. 1 (errata: fig. 2)]
1839 Pecten marylandicus Wagner, 1839
W. Wagner, 1839, plate 1.
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«Shell ovate, compressed; ribs numerous, consisting of narrow, nearly smooth striae, disposed in pairs; interstitial spaces each with a carinated line; ears unequal ; inferior valve very slightly convex; ribs similar to those of the opposite valve; inner margin of the valve with profoundly elevated lines.
Locality. Mehering river. North Carolina. This Pecten is allied to PECTEN Madisonius, Say, but can readily be distinguished by its want of broad, elevated ribs, and a surface destitute of scales; several specimens of SPIRORBUS nautiloides, Lam., are attached to the surface of the superior valve.» WILLIAM WAGNER, 1839
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«Discussion.— Some specimens of Chesapecten (Christinapecten) marylandica appear to intergrade with specimens of Chesapecten (Chesapecten) nefrens with which it co-occurs, but close inspection makes the two separable on the basis of rib numbers and shape as well as scaling patterns. Chesapecten (C.) maryIandica has scaly auricles but lacks scales on the disk except on the most anterior and/or most posterior ribs. The habit of bifurcation of ribs produces a very uniformly fine radial sculpture that is easily recognized.
Pecten marylandicus was named by Wagner (1839) and was reported to have come from the "Mehering river, North Carolina." Valves of "Pecten" decemnaria which are similar to Chesapecten (Christinapecten) marylandica, but belong to another distinct lineage, are present in the Rushmere Member of the Yorktown Formation at Murfreesboro, N.C., in exposures along the Meherrin River. They are easily distinguished from the C. (C.) marylandica because they lack the "smooth striae, disposed in pairs" and "interstitial spaces each with a carinated line" that Wagner described (1839, p. 51). It is immediately suspicious, but not impossible, that Wagner meant to name a North Carolina pectinid "marylandica." The remainder of the taxa described by Wagner could have all come from the Choptank River on the Patuxent River, St. Marys County, Md., and indeed one, Trochus eboreus, was described from there. I believe that C. (C.) maryIandica did, in fact, come from that locality in Maryland. The whereabouts of Wagner's type material is unknown, and I herein designate the specimen illustrated on Plate 16, figure 1 (USNM 405211), as the neotype. Type information.— Neotype: USNM 405211. Type locality: Drumcliff Member of the Choptank Formation at Drumcliff (Jones Wharf) on the Patuxent River, St. Marys County, Md. Probably the type locality. Figured specimen.— Neotype (USNM 405211) from Drumcliff (Jones Wharf) on the Patuxent River, St. Marys County, Md. (locality 16). Stratigraphic and geographic range.— Choprank Formation, Drumcliff Member (Bed 17) (middle middle Miocene) in Maryland. Calvert Formation, Calvert Beach Member (lower middle Miocene) in Maryland and Virginia.» WARD, L. W. 1992. Molluscan bioestratigraphy of the Miocene, middle Atlantic Coastal Plain of North America. Memoirs of the Virginia Museum of Natural History, 2: 1-159, pls. 1-26. [p. 74]
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Chesapecten (Christinapecten) marylandica (Wagner, 1839); L. W. Ward, 1992, Molluscan bioestratigraphy of the Miocene, middle Atlantic Coastal Plain of North America, plate 16, figure 1.
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«In external ornamentation the species ranges from individuals showing uniform radiating lirae similar to those of Placopecten clintonius —though stronger and consequently less numerous— to individuals exhibiting true ribs that recall those of Lyropecten and that are sufficiently strong to crenulate the interior of the valves. The ribs do not, however, become so strong as in the typical madisonius, nor are they ever reduced to interareas between impressed lines, as in virginianus and certain representatives of tenuis. The delicate, concentric sculpture is visible in the interspaces, as in clintonius, but it does not imbricate the radial striations, as in many individuals of tenuis.
Distribution: Virginia: Miocene, Choptank formation, Nomini Cliffs, Westmoreland County.
Outside distribution: Miocene, Choptank formation, Dover Bridge, Queen Annes County, Md.; Governor Run, Flag Pond, and St. Leonard Creek, Calvert County, Md.; Jones Wharf, Patuxent River, St. Marys County, Md.» GARDNER, J. 1943. Mollusca from the Miocene and lower Pliocene of Virginia and North Carolina. Part 1. Pelecypoda. United States Geological Survey Professional Paper, 199-A: 1-178, pls. 1-23. [p. 38]
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Chlamys (Placopecten) marylandica (Wagner) Glenn; J. Gardner, 1943, Mollusca from the Miocene and lower Pliocene of Virginia and North Carolina, plate 5, figure 4; plate 6, figures 2, 3.
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