"Chlamys" deshayesii (Lea, 1833)
LEA, I. 1833. Contributions to geology. vi, 227 p., pls. 1-6. Carey, Lea and Blanchard. Philadelphia, 1833. [p. 87, pl. 3, fig. 66]
1833 Pecten deshayesii Lea, 1833
1833 Pecten minutus Lea 1833 [nomen nudum]
1833 Pecten lyelli Lea, 1833
1934 Chlamys (Chlamys) deshayesi dennisoni Tucker-Rowland, 1934
1890 Pecten deshayesii mut. tirmus Gregorio, 1890
1833 Pecten minutus Lea 1833 [nomen nudum]
1833 Pecten lyelli Lea, 1833
1934 Chlamys (Chlamys) deshayesi dennisoni Tucker-Rowland, 1934
1890 Pecten deshayesii mut. tirmus Gregorio, 1890
I. Lea, 1833, plate 3.
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«Description. Shell orbicular, rather compressed ears nearly equal; substance of the shell rather thick; ribs about twenty-one, large, alternating with as many small ones, all imbricate; beaks pointed.
Diam...... Length 1.3, Breadth 1.3, of an inch. Observations. I know no species which this resembles so much as the gracilis (Sowerby), from the Crag at Holywells. It differs in having rather large ribs instead of "many small longitudinal ridges."» ISAAC LEA, 1833
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«DESCRIPTION.— Lea's original description:
"P. Deshaysii: Shell orbicular, rather compressed; ears nearly equal; substance of the shell rather thick; ribs about twenty-one, large, alternating with as many small ones, all imbricate; beaks pointed. " Additional observations by Tucker-Rowland, 1936: "Holotype of dehayesi Lea, an orbicular, somewhat convex left valve, has a height of 33 and width of 32 mm. About 20 primary, uniform, rounded radials. One major intercostal; sometimes one or two minor ones appear about 18 mm from the margin. Concentric lamellae reflected beakward as they cross the radials. Nearly equal, radially threaded auricles. Internally, obsolete ribs are stronger at the margins than umbonally." OCCURRENCE IN GEORGIA.— Chlamys deshaysi is common in the lowest beds encountered at Georgia Rock Products Company quarry, Arlington (locality 24). These beds also contain Periarchus lyelli (Conrad) and are probably equivalent to the lower member of the Moodys Branch Marl (Paul Huddlestun, personal communication, 1972). C. deshaysi has been reported from the Moodys Branch on the east bank of the Chattahoochee River about 2 miles above U. S. Highway 84 bridge (Toulmin and LaMoreaux, 1963). DISTRIBUTION ELSEWHERE IN THE SOUTHEASTERN UNITED STATES.— Chlamys deshaysi is known from numerous Middle and Upper Eocene localities in Mississippi and Alabama (Type, Claiborne Bluff on the Alabama River (locality 13)). REMARKS.— Chlamys deshaysi and Chlamys cawcawensis (Harris) frequently occur in the same beds at localities in Alabama and many workers lump both forms together as C. deshaysi. However, C. cawcawensis is restricted to the Upper Eocene (at least in Alabama) and the two species can be distinguished on the basis of differences in right valve external ornamentation. Right valves of C. cawcawensis have wide, smooth ribs with lirae on the interspaces only, whereas right valves of C. deshaysi have lirae on both the ribs and interspaces. Left valves of the two species have lirae on both the ribs and interspaces and are not significantly different. The difference in number of ribs observed in C. cawcawensis as compared with C. deshaysi is very small and pro bably insignificant. Typically C. cawcawensis has about 23 ribs; however at Double Bridges Creek near Geneva, Alabama (locality 19) in a sample containing 14 right valves of C. cawcawensis, the number of ribs on the disk varies from 13 to 25 and averages 17.7. In a sample of 59 specimens of C. deshaysi from High Bluff on the Choctawhatchee River near Geneva, Alabama (locality 20), the number of ribs on the disk varies from 15 to 23 and averages 19.1.» 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. 7, 8]
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Chlamys (Aequipecten) deshaisy (Lea); L. N. Glawe, 1974, Upper Eocene and Oligocene Pectinidae of Georgia and their stratigraphic significance, plate 3, figures 7, 8, 10.
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«There seems to be considerable uncertainty as to what, and how many species of Pecten really come from the Claiborne sands. Dall says regarding deshayesii (Trans. Wag., Ill, p. 738):
"This species is positively known to occur in the Jacksonian at Claiborne and elsewhere, but I have obtained no specimens from the vast amount of marl belonging to the true Claiborne sands horizon which has come under my notice."
Cossmann finds this species "excessivement rare" in his barrel-full of sand.
Our various collection at the same horizon and place, whenever at all extensive, have never failed to produce several good specimens of Pecten of this and perhaps other nearly related forms. The specimens of this so-called species found in famous "sands" are very variable in outline, size and markings. What one usually finds is just what Lea described: one or more large left valves, quite highly ornamented, along with smaller right valve with simpler ribbing. The right valves seem more elongate, just as Lea remarks under his lyelli. Along with these, one generally .secures fragments, at least, of large right valves with flat, smooth, broad ribs, regarded by some as having been worn. (See pl. 13, fig. 8.) The right valve while young possesses a very prominent anterior byssal ear with a deep notch, and a broad shallow groove extending to the beak, also about 5 imbricate rays; posterior ear much smaller, forming an angle of approximately 90 degrees with the hinge line and having about 5, often double, rays; general shell surface with ribs equalling interspaces in width, about 18 well defined ribs on the face of the shell, with half a dozen or so fine radiating lines or subdivided riblets on the lateral umbonal margins; surface ornamentation, imbricate concentric lines; ribs often showing an incilnation to bifurcate on marginal areas, at least a deeply incised line is often seen on the tops of the ribs in these regions; near basal margin there is a tendency to show obscurely, however, three raised lines on top of main ribs and one or three lines in the inter-costal area. Left valve while young showing markings similar to those described above, with more nearly equal ears, however, and a tendency to show at an earlier age three lines on top of the ribs; and a strong line (often between two others) between the ribs, irregularities like subdivision of costae, increasing comparative width of interradial spaces, great increase in radiating, fimbriate lines on top of ribs on their sides and in interspaces, apparent; shell deepening rapidly with age. Occasionally on certain portions of the exterior of the left valve a strong bi-partite structure is seen in the ribbing. This has given rise to the varietal name tirmus by de Gregorio. We do not think it of even varietal rank. Concerning the type of deshayesi in the Phila. Acad, it may be noted that it shows 20-22 primary, with as many inter-ribs; the latter apt to be on the anterior side of the intercostal space; traces of tertiary riblets; few signs of riblets superimposed on primary ribs; finely, evenly crinkled, concentric incised lines on ears. The type specimen of lyelli has about an equal number of ribs; but slight traces of intercostse and concentric line; ribs not showing bifurcation as plainly as is indicated by fig 7, pl. 13 of this work. Types.— Philadelphia Acad. Coll., Cat. Nos. 5425, 5426. Localities and Horizon.— Typically in the Claiborne sand horizon. A specimen seemingly of the lyelli form is in our collection from the Orangeburg district, S. C. Specimens figured.— Collections at Cornell Univ.» HARRIS, G. D. 1919. Pelecypoda of the St. Maurice and Claiborne Stages. Bulletins of American Paleontology, 6 (31): 5-268, pls. pls. 1-59. [p. 20, 21]
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Pecten deshayesii Lea; G. H. Harris, 1919, Pelecypoda of the St. Maurice and Claiborne Stages, plate 13, figures 2-7.
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