Euvola heimi (Hertlein, 1925)
HERTLEIN, L. G. 1925. Pectens from the Tertiary of Lower California. Proceedings of the California Academy of Sciences, 4th series, 14(1): 1-35, pls. 1-6. [p. 9, pl. 1, fig. 3; pl. 3, fig. 3]
1925 Pecten (Pecten) heimi Hertlein, 1925
L. G. Hertlein 1925, plates 1, 3.
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«Shell concavo-convex, equilateral, inequivalve. Right valve highly arched, and ornamented by about 20 or 21 rounded, radiating ribs which become flattened toward ventral margin, these separated by round-bottomed interspaces about one-half as wide as the ribs; ribs and interspaces crossed by concentric incremental lines of growth; ventral margin of shell rounded; ears somewhat convex; a distinct groove on right ear close to margin of shell, and byssal notch also present ; anterior margin of right ear somewhat convex; ear ornamented by about four or five radiating riblets and by concentric incremental lines. Left valve slightly concave and ornamented by about 17 or 18 radiating ribs which are separated by round-bottomed interspaces, the ribs and interspaces crossed by fine concentric incrementallines; a depressed area present just below the beaks; anterior and posterior margins of valve flattened, higher than the depressed inner area near beak, sloping abruptly to ears; ears concave and sculptured by fine incremental lines only.Altitude 75 mm.; longitude 85 mm.; diameter of right valve approximately 25 mm.; apical angle of right valve approximately 97°.
Type: Right valve, No. 46 (L.S.J.U. type collection), from Loc. 65 (L.S.J.U.), southern part of Arroyo San Gregorio, Lower California; Paratype: No. 47 (L.S.J.U. collection), E. R. Swarts and T. J. Cullen collectors; Lower Pliocene? Pecten heimi differs from P. hemphillii Dall in the number of ribs, which is greater in P. heimi, and in the ears which are smooth, and more convex in the present species than in P. hemphillii. From P. coalingensis Arnold and P. auburyi Arnold it is distinguished by its larger size and the more rounded shape of its ribs; from P. vogdesi Arnold, by the fact that the shell in P. heimi does not flatten out at the ventral margin as does P. vogdesi, and P. heimi has a greater number of ribs than Arnold's species. P. heimi differs from P. hartmanni Hertlein, in being longer in proportion to the altitude, less inflated, and in possessing differently shaped ears. From P. aztecus Böse, P. heimi is distinguished by the fewer, more rounded, broader ribs, in the present species; furthermore, P. heimi is larger and apparently more convex. This species is named in honor of Dr. Arnold Heim, whose work has added much to the knowledge of the geology of Lower California.» LEO GEORGE HERTLEIN, 1925
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