Leptopecten tolmani (Hall & Ambrose, 1916)
HALL, E. B. & A. W. AMBROSE. 1916. Descriptions of new species from the Cretaceous and Tertiary of the Tesla, Pleasanton, San Jose, and Mt. Hamilton quadrangles, California. The Nautilus, 30 (6): 68-71; 30 (7): 77-82. [p. 82]
1916 Pecten tolmani Hall & Ambrose, 1916
Pecten tolmani Hall and Ambrose; L. W. Wiedey, 1929, Some previously unpublished figures of type mollusks from California, plate 1, figure 2.
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«Description. Both valves convex, left more convex of two, inequilateral, base regularly rounded; margins smooth. Right valve with 16 to 18 prominent rounded ribs, separated by rounded interspaces, narrower than the ribs; ribs on left valve more prominent and irregularly spaced; surface sculptured by numerous, fine, imbricating, regular lines of growth; hinge line less than one-half length of disk; ears subequal; anterior ear of other specimens show 5 or 6 sharp radial lines emanating from beak, crossed by fine, faint, concentric lines; sculpture of posterior ear less distinct but truncated at right angles.
Dimensions. Alt. 67 mm.; long. 71 mm.; diameter 9 mm.; umbonal angle 130º. Notes. This species resembles an enlarged P. andersoni but is undoubtedly a new form. This form is much larger than P. andersoni, the hinge (proportional to size) much shorter, and the umbonal angle much larger. It is possible this form is a descendant of P. andersoni, of Monterey times. The young are very similar to P. andersoni, and it is not certain that the forms classified as P. andersoni in the Briones are not the young of P. tolmani. Named in honor of Prof. Cyrus Fisher Tolman, Jr. Type. Museum, Stanford University, Calif. Locality. Briones of Tesla, Pleasanton, San Jose and Mt. Hamilton Quadrangles. Horizon. Brionet, Middle Miocene ; probably Monterey, Lower Miocene.» HALL, E. B. & A. W. AMBROSE, 1916
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«Comments.— The holotype is a large (for the genus), moderately inflated left valve. The umbonal angle is small, the umbo inflated, and the beak higher than the hinge line. Although the umbonal angle is small and the line of attachment of the auricles to the disk steeply concave, the shell then flares outward toward the anterior and posterior margins in a line subparallel to the hinge, and in this character resembles P. weaveri. The ribs on P. tolmani are subrounded, not prominent, and are separated by wider interspaces at the ventral margin. The anteriormost and posteriormost margins of the shell bear only faint traces of ribs. The valve seems to have been inequilateral with the anterior portion larger than the posterior.
The left valve holotype of P. tolmani, is twice as large as the left valve syntype of P. weaveri, and has 17 low rounded ribs. Pacipecten weaveri has 14 ribs on the leftvalve syntype and these ribs are higher and more ridgelike than those on P. tolmani. In addition, P. weaveri does not have the slightly sculptured areas at the anterior and posterior margins. Pacipecten weaveri has fine concentric lamellae on the left valve that may be bunched together giving a roughness to the ribs; P. tolmani has an almost smooth left valve with barely perceptible concentric lines. Geographic range.— Middle California. Geologic range.— Miocene. Occurrence in California.— Briones (Hall, 1958) and Cierbo (Huey, 1948) Sandstones.» MOORE, E. J. 1984. Tertiary Marine Pelecypods of California: Propeamussidae and Pectinidae. United States Geological Survey Professional Paper, 1228-B: iv + B1-B112, figs. 1-2, pls. 1-42. [p. B46]
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Pacipecten tolmani (Hall and Ambrose); E. J. Moore, 1984, Tertiary Marine Pelecypods of California: Propeamussidae and Pectinidae, plate 14, figure 2.
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