Pecten (Propeamusium) [sic] vacavillensis D. B. K. Palmer, 1923
PALMER, D. B. K. 1923. A fauna from the middle Eocene shales near Vacaville, California. University of California Publications, Bulletin of the Department of Geological Sciences, 14 (8): 289-318, pls. 52-57. [p. 301, pl. 55, figs. 3-5]
«PECTEN (PROPEAMUSIUM) VACAVILLENSIS n. sp.
Plate 55, figures 3, 4a, 4b, and 5 Holotype.— No. 30596, Univ. Calif. ColI. Invert. Pal.; Univ. Calif. locality 3573.
Paratype.— No. 30597, Univ. Calif. ColI. Invert. Pal.; Univ. Calif. locality 3573. Paratype.— No. 30708, Univ. Calif. ColI. Invert. Pal.; Univ. Calif. locality 3573. Shell very small; hinge line straight; anterior dorsal nlargin slightly concave; posterior dorsal margin broken on holotype but straight on paratypes. Ventral margin gently rounded. Ventral edge of shell very thin and for this reason usually broken. Anterior ear separated from the main surface of the shell by a rather strong flexure; only a very slight concavity bet,ween posterior ear and main surface of shell. Ventral two-thirds of external surface of holotype ornamented with very fine concentric striae and fine, closely spaced radial striae. Dorsal third of external surfaee of holotype smooth with the exception of several widely spaced concentric grooves. Entire external surface of paratype No. 30597, a right valve, ornamellted with fine concentric striae which are usually more prominent than those on the holotype. Radial striae lacking. Interior of holotype with 8 evenly spaced, prominent, rounded ribs which commence about a third the height of the shell below the beak and extend almost to the ventral margin. Intorspaces flat. Dimensions of holotype (a left valve): Height 1.4 mm.; length (ventral edge slightly broken) 1.44 mm.
Occurrence.— P. vacavillensis is one of the most common forms in the shales near Vacaville. Univ. Calif. locality 3575, Middle Eocene, near Vacaville, California. P. vacavillensis n. sp. differs from P. interradiatus Gabb [20] in that the internal ribbing occupies only the ventral two-thirds of the shell instead of the dorsal half as indicated in the original figure. P. vacavillensis n. sp. may be distinguished from the form from Coalinga figured by Arnold [21] by the fact that the external radial striae, when present, are closely spaced.»
[20] Gabb, Op. cit., vol. 2, p. 199, pI. 33, figs. 98, 98a, 1869.
[21] Arnold, R., U. S. G. S. Bull. 396, pI. 3, figs. 7 and 11, 1909. DOROTHY BRYANT KEMPER PALMER, 1923
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D. B. K. Palmer, 1923, plate 55.
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