Euvola hemicyclica (Ravenel in Tuomey & Holmes, 1855)
TUOMEY, M. & F. S. HOLMES. 1855-1856. Pleiocene fossils of South Carolina. Russell and Jones, Charleston, South Carolina, i-xvi + 1-152 pp., pls. 1-30. [p. 25, pl. 8, figs. 1-4]
1855 Janira hemicyclica Ravenel in Tuomey & Holmes, 1855
1932 Pecten (Pecten) ochlockoneensis Mansfield, 1932
1939 Pecten (Pecten) ochlockoneensis leensis Mansfield, 1939
1932 Pecten (Pecten) ochlockoneensis Mansfield, 1932
1939 Pecten (Pecten) ochlockoneensis leensis Mansfield, 1939
M. Toumey & F. S. Holmes, 1855-1856, plate 8.
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«J. testa sub-semicirculari, depressa; concentrice striata, inaequivalvi, aequilaterali; valva inferiore convexa; costis marginem versus sulcatis; valva superiore depressa, costis convexis, sub-inaequalibus.
DESCRIPTION. Shell somewhat semi-circular, depressed, striated concentrically and closely; inequivalve, equilateral, lower valve convex, ribs, towards the pallial margin, turned up and sulcate; upper valve depressed, or flat, concave towards the pallial margin, ribs convex; buccal ears depressed, lower one with a stout ridge. This fine fossil has its living representative in JANIRA (PECTEN) JACOBAEA, which it greatly resembles, and from which it is distinguished by its less convex lower valve, and by the absence of the radiating and numerous impressed lines of the ribs. PLATE VIII., FIG. 1. Upper valve, natural size. " 2. Lower valve. " 3. Side view of fossil. " 4. Outline of the ribs. LOCALITY. Grove, Cooper River. Museum, College of Charleston, S. C.»
MICHAEL TUOMEY & FRANCIS SIMMONS HOLMES, 1855
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«Description: Shell large, subcircular, inequivalve, upper valve nat to weakly concave, lower valve convex, shallow in juvenile and typical adult specimens; ribs 20, low, with wider interspaces on upper valve. Very large specimens becoming laterally elongate, with the lower valve deeply cupped, the ventral margin of lower valve overlapping the upper valve.
Occurrence: Pliocene. Virginia – Yorktown, Zone 2; South Carolina – lower Goose Creek Limestone (common), upper Goose Creek Limestone (rare), Raysor (rare); Florida – Pinecrest and Jackson Bluff. Type locality: The Grove Plantation, Charleston, South Carolina. Discussion: Pecten hemicyclicus changed shape during ontogeny. Very large, laterally elongated shells, such as the type specimen, are not uncommon at Goose Creek localities but are rare in Florida. The smaller, more circular Florida specimens were named Pecten ochlockoneensis Mansfield, 1932, and Pecten ochlockoneensis leensis Mansfield, 1939. Reports of this species in the upper Pliocene Waccamaw Formation (Gibson, 1987, p. 41) or Recent (Dall, 1889, p. 32) appear to be incorrect, the Waccamaw report resulting from stratigraphic confusion, and the Recent report from misidentification.
Abbott (1974, p. 442) defined the subgenus Euvola as follows: "Lower or right valve very convex and with weak, rounded ribs; upper or left valve quite flat, more heavily sculptured. Type: ziczac (Linnaeus, 1758)." Fossil and Recent Pecten (Euvola) species are confused in both historic and current literature. In addition to Pecten hernicyclicus and its synonyms, there are Pecten ziczac (Linnaeus, 1758), Pecten brouweri Tucker, 1934 (see plate 5, figures 4 and 5), and two species covered under Pecten raveneli Dall, 1898. Pecten ziczac, a Recent species, has 18 to 20 very low ribs with strong secondary ribbing in the interspaces. The right valve is convex but shallow. Its ribbing is distinct from that of the remaining taxa in which the interspaces lack the broad secondary ribbing. Its ribs are more elevated, and they are commonly grooved on the right valve. Recent shells called Pecten raveneli resemble P. ziczac and P. hemicyclicus in the shallow convexity of the right valve, but the Recent P. raveneli averages 25 ribs in contrast to about 20 ribs for P. hernicyclicus. The holotype of P. raveneli is a fossil from the "Caloosahatchee marls." Dall's figure (Dall, 1898, pI. 29, fig. 10) shows a substantially more convex shell, especially in the early growth. Fossil specimens of P. raveneli average 21 to 22 ribs. The Recent "P. raveneli" seems to be unnamed; it is being studied by Thomas Waller of the Smithsonian Institution. Pecten brouweri differs from P. raveneli in having 14 to 16 ribs (Tucker, 1934). In outline, convexity of right valve, and absolute size attained, P. brouweri is very close to the holotype of P. raveneli. Pecten brouweri is known from only a few specimens. All recovered in South Carolina are from the Goose Creek Limestone, considerably older than the "Waccamaw" age reported by Tucker (1934). Its rarity seems to be related to past unavailability of Goose Creek age deposits. The small population of P. brouweri in hand has a range of rib numbers from 14 to 20, placing it in close conformity with P. raveneli. Pecten brouweri is probably only subspecifically distinct from true P. raveneli, if not fully conspecific. Resolution of the problem will require larger populations than are now available. Pecten ochlockoneensis violae Tucker, 1936, is here elevated to species status. Pecten violae is larger than P. raveneli and P. brouweri. The upper valve is concave for the first 10 mm of the disk, then becomes nearly flat. The upper valves of P. raveneli and P. brouweri are evenly concave across the entire disk. Typical specimens of P. violae have 15 to 16 radial ribs.» CAMPBELL, M. R. & L. D. CAMPBELL. 1995. Preliminary Biostratigraphy and Molluscan Fauna of the Goose Creek Limestone of Eastern South Carolina.Tulane Studies in Geology and Paleontology, 27 (1-4): 53-100, pls. 1-5. [p. 70, 72]
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Pecten hemicyclicus Ravenel; M. R. Campbell & L. D. Campbell, 1995, Preliminary Biostratigraphy and Molluscan Fauna of the Goose Creek Limestone of Eastern South Carolina, plate 1, figure 5; plate 3, figure 6.
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«36. Pecten hemicyclicus (Ravenel, 1834) (Synonyms: Pecten ochlockoneensis Mansfield, 1932; Pecten ochlockoneensis leensis Mansfield, 1939; Pecten raveneli (Dall) of Cooke, 1936, and of Campbell and others, 1975, not of Dall, 1898). Shell of medium size, with about 22 radial ribs; ribs wider and stonger centrally, smaller, weaker, and more closely spaced laterally. A smaller radial intenib is occasionally developed in the interspaces. Concentric sculpture of very fine, evenly raised lines. Byssal notch present. Zone 2, Chuckatuck crossbeds. Length 62 mm, height 54 mm. This species is very rare in the Yorktown, and only the left or flat valve has been recovered. Pecten hemicyclicus is proportionally wider than Pecten raveneli and has shallower interspaces. The two have frequently been confused in the literature.»
CAMPBELL, L. D. 1993. Pliocene molluscs from the Yorktown and Chowan River Formations in Virginia. Virginia Division of Mineral Resources Publication, 127: 1-259, pls. 1-43. [p. 23]
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Pecten hemicyclicus; L. D. Campbell, 1993, Pliocene molluscs from the Yorktown and Chowan River Formations in Virginia, plate 4, figure 36.
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«Two valve of the same individual in he U. S. National Museum, Cat. No. 15467, identified by F. S. Holmes, have this label:
This is on of the only three perfect specimens that has ever been found of this fossil. It was named and described by Dr. Ravenel of this place, from odd valves. It is but Iately that I was fortunate in finding them in juxtaposition.
Right valve very convex; radial sculpture of 17 flat-topped ribs which develop sulci on their summits near the ventral margin. Whole valve concentrically sculptured by elevated, widely spaced lamellae. Submargins and auricles sculptured only by the more closely spaced, elevated, concentric lamellae. Byssal flexure slight. Provinculum; auricular crura. Left valve has 17 ribs which become nearly obsolete in the concave umbonal area. Concentric sculpture similar to tha of the right valve.
In the collections of the Academy of Natural Sciences of Philadelphia are two imperfect valves of this species which are very nearly identical with those in the U. S. National Museum. Dimensions: Right valve, height 57, width 65 mm.; left valve, height 56, width 64 mm.; hinge 28 mm. The label is marked "S. Car.". Dimensions of neoholotype.— Rihgt valve, heigh 95, width 115 mm.; left valve, height 95, width 112 mm; hinge 52 mm.; diameter 35 mm. Localities.— Grove, Cooper River, S. C. (type?); Goose Creek at Smiths, S. C. (neoholotype), Ravenel, Tuoumey and Holmes. Horizon.— Waccamaw (Pliocene). Neoholotype.— Right and left valves of the same individual, deposited in U. S. NationaI Museum, Cat. No. 15467.» TUCKER-ROWLAND, H. I. 1936. The Atlantic and Gulf Coast Tertiary Pectinidae of the United States. The American Midland Naturalist, 17: 471-490, pls. 1-4 [Under H. I. Tucker]. [p. 484]
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Pecten (Pecten) hemicyclicus Ravenel; H. I. Tucker-Rowland, 1936, The Atlantic and Gulf Coast Tertiary Pectinidae of the United States, plate 2, figure 5; plate 3, figure 1.
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