Mesopeplum subconvexum (Tate, 1887)
TATE, R. 1887. The Lamellibranchs of the Older Tertiary of Australia, Part II. Transactions and Proceedings and Report of the Royal Society of South Australia, 9: 142-189 [p. 185, pl. 18, fig. 2]
1887 Pecten subconvexus Tate, 1887
R. Tate, 1887, plate 18.
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«Irregularly orbicular, moderately convex, produced in front, radially ribbed. Ribs about 27, broad, truncated, considerably elevated, becoming thinner and subacute towards the sides; an indistinct appearance of three radial plications is produced by thicker ribs occurring close together in pairs. The interspaces between the ribs are as wide or a little wider than the ribs; they are concentrically sulcate, the intervening elevated threads are about equal in width to the sulci. Ears ? Margin of the valve crenately undulate.
Dimensions.— Antero-posterior diameter, 30·5; umbo-ventral diameter, 31·5; sectional diameter of right valve, 5·5 millimetres. Locality.— Upper beds at Muddy Creek (J. Dennant !). Amongst recent species P. subconvexus is most nearly related to P. convexus, Quoy and Gaimard, from which it differs by the absence of radial folds, and the fewer, more distant, and flatter ribs; it is, moreover, less inflated. In a lesser degree it resembles P. polymorphoides, Zittel, which occurs at a lower geological horizon.» RALPH TATE, 1887
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