"Chlamys" spillmani (Gabb, 1860)
GABB, W. M. 1860. Descriptions of new species of American Tertiary and Cretaceous fossils. Journal of the Academy of Natural Sciences of Philadelphia [2nd Series], 4 (4-14): 375-406, pls. 67-69 [p. 402, pl. 68, fig. 3]
1860 Pecten spillmani Gabb, 1860
G. W. Gabb, 1960, plate 68.
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«P. SPILLMANI. PI. 68, fig. 3. Equivalve, orbicular; surface marked by about twenty-two radiating ribs, each with one or two very small ones on each side, and with the crests of all minutely granulous; alations ? (both ears are broken in the specimen before me).
Locality.— Eocene. Alabama. Dr. Spillman.» WILLIAM MORE GABB, 1860
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«DIAGNOSIS.— Populations of the C. clinchfieldensis stock containing smooth and multilirate-ribbed forms in which more than 75 percent of the individuals have lirae on the ribs prior to the 25 mm-in-height growth stage. It differs from Chlamys nupera (Conrad) in having a coarser, more pronounced ornamentation on the main and lateral lirae on the ribs.
DESCRIPTION.— Gabb's original description: "Equivalve, orbicular; surface marked by about twenty-two radiating ribs, each with one or two very small ones on each side, and with the crests of all minutely granulous; alations ? (both ears are broken in the specimen before me). Locality, Eocene, Alabama. Dr. Spillman." Shell orbicular, suborbicular in unusually large specimens, small, maximum height 39.5 mm (generally about 30 mm), maximum length 43.6 mm (generally about 30 mm), mean height and length 22.2 mm, moderately thick, equally convex valves; hinge line slightly concave in right valve, nearly straight in left valve; ribs near beak are low and smooth, then lateral lirae are added on the sides of ribs and increase in numbers with increase in size of shell, lirae extend into interspaces on large specimens; concentric lamellae crossing lirae exhibit pronounced outgrowths; right valve with 22 to 26 ribs (mean 23.7), left valve with 21 to 26 ribs (mean 23.3). Ears fairly small subequal anterior ear longer than posterior ear, prominently striated with 4 to 9 radial threads; byssal notch deep; ctenolium with 2 to 4 teeth exposed. Hinge with provinculum and 2 pair of cardinal crura; resilial pit with ridge along anterior margin in the right valve. Interior of valve with faint internal ribs fluted along the ventral margin. Description based primarily on 100 specimens from the Pachuta Marl Member of the Yazoo Formation at Lone Star Cement Company quarry near St. Stephens, Alabama (locality 9). DIMENSIONS.— Holotype (Academy of Natural Sciences, Philadelphia) double valve: height 28.1 mm, length 29.0 mm, convexity 12.5 mm, from Shubuta, Mississippi. OCCURRENCE IN GEORGIA.— Rare in Ocala Limestone at abandoned quarry on Oakland Plantation near Albany (locality 25) and along Muckafoonee Creek below Power Plant dam near Albany (locality 26), and common in upper part of Ocala Limestone at Medusa Portland Cement Company quarry near Clinchfield (locality 29). DISTRIBUTION ELSEWHERE IN THE SOUTHEASTERN UNITED STATES.— Very abundant in most of the Upper Eocene calcareous units of eastern Mississippi (Pachuta Marl), Alabama (Cocoa Sand, Pachuta Marl, and Ocala Limestone), and Florida (Ocala Limestone).» GLAWE, L. N. 1974. Upper Eocene and Oligocene Pectinidae of Georgia and their stratigraphic significance. Geological Survey of Georgia, Information Circular, 46: 1-27, pls. 1-4. [p. 4, 6]
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Chlamys (Aequipecten) spillmani (Gabb); L. N. Glawe, 1974, Upper Eocene and Oligocene Pectinidae of Georgia and their stratigraphic significance, plate 3, figures 1-3; plate 4, figures 1, 3.
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