Chlamys (Plagiotecnium) comparilis jacksonensis Mansfield, 1932
MANSFIELD, W. C. 1932. Miocene Pelecypods of the Choctawhatchee Formation of Florida. Florida Geological Survey Bulletin, 8: 7-164, pls. 1-34. [p. 62, pl. 8, figs. 4, 5]
«Chlamys (Plagioctenium) comparilis jacksonensis
Mansfield, n. subsp. Plate 8, Figures 4, 5 SheIl of moderate size, suborbicular in outline, both valves equally convex, inequilateral — the posterior region being more produced. Right valve sculptured with 21 moderately narrow, elevated ribs subrounded above and nearly flat below and separated by deep interspaces that are a little wider than the ribs. The distal end of each rib has a raised median thread. Left valve similarly sculptured to right. Concentric sculpture on the disk of both valves consists of scaly, rather coarse lamellae. Right and left submargins steeply inclined and sculptured only witlh closely set concentric lamellae. Anterior ear a little longer than posterior, sculptured with four moderately strong radials and transverse lamellae. Surface of posterior ear marked with about two more radials than anterior. Byssal notch moderately deep.
Cotypes (Cat. No. 371141, U. S. N. M.) measure: Right valve: Length, 46 mm.; height, 43, mm.; diameter, 12 mm. Left valve: Length, 49 mm.; height, 44 mm.; diameter, 13 mm. The new subspecies differs from C. comparilis in having a proportionately longer shell. It also has about one less rib. The number of ribs on ten right valves is as follows: One with 23, six with 22, two with 21, and one with 20; the average number, therefore, is about 22. The numher of ribs on five left valves is as follows: One with 23, two with 22, two with 21; the average number is about 22. The average number of ribs on C. comparilis is about 23. Occurrence: Upper Miocene: Ecphora zone — station 3423, lower upper Miocene bed at Jackson Bluff, Leon County, Fla., type locality; Clarksville, Calhoun County. Ecphora or Cancellaria zone — station 1/951, Red Head Still, Washington County (specimens poorly preserved, identification uncertain).» WENDELL CLAY MANSFIELD, 1932
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W. C. Mansfield, 1932, plate 8.
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