Nanaochlamys nutteri (Arnold, 1906)
ARNOLD, R. 1906. The Tertiary and Quaternary pectens of California. United States Geological Survey Professional Paper, 47: 1-264, 53 pls [p. 67, pl. 11, figs. 3, 4, 4a]
1906 Pecten (Chlamys) nutteri Arnold, 1906
R. Arnold, 1906, plate 11.
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«Description.— Shell averaging about 65 millimeters in altitude, slightly higher than long, inequivalve, equilateral, more or less ventricose, and often showing several constrictions or undulations of interrupted growth; margins somewhat coarsely serrate; base regularly rounded; sides straight, and forming an acute angle at the umbo. Right valve with about 8 to 10, unequal, rather prominent, flat-topped ribs, each of which is channeled by one or more deep, narrow, concave sulcations which divide the primary rib from umbo to margin into two or more generally unequal but evenly convex riblets; interspaces somewhat narrower than the ribs, and containing from 1 to 3 prominent rounded riblets; the riblets become more numerous and the major ribs less prominent anteriorly and posteriorly; the minor sculpture consists of squamose lines of growth, which are more prominent on the ribs, and beautiful microscopic checkered tessellation which is best developed in the major and minor interspaces; hinge line from two-fifths to nearly one-lialf length of disk; anterior ear prominent and sculptured by 5 or 6 elevated radiating ridges and imbricating concentric lamellae; byssal notch moderately deep; posterior ear rectangularly truncated, a little less than one-half length of anterior, and similarly but less prominently sculptured. Left valve with unequal, rather narrow, convex ribs, the alternate ones being more prominent than those intermediate; extremities of the ribs sometimes ornamented by longitudinal riblets; interspaces of about equal width to the ribs, and ornamented by one or three alternately prominent intcrcalaries; surface sculptured by imbricating incremental lines; the constrictions, when present, are more pronounced in this valve; ears sculptured similarly to those of the right valve. Hinge with a pair of prominent cardinal crura adjacent to the umbonal pit in the right valve.
Dimensions.— Alt. 64 mm.; long. 57 mm.; hinge line 27 mm.; diameter 21 mm. This species is allied to P. parmeleei and P. wattsi but is distinguishable by having a larger number of ribs, which are also narrower and more coarsely radially sculptured. The Miocene forms of P. nutteri have more prominent and deeply sulcated ribs on the right valve, are generally more convex and more prominentiy constricted, and have relatively longer posterior ears than the later forms. P. nutteri so far as known, ranges from the Mount Hamilton Range Miocene to the lower Pliocene. It is found rather abundantly in a certain layer in the sea cliff, one-half mile south of the mouth of San Gregorio Creek, San Mateo County, associated with a characteristic lower Pliocene (Purisima) fauna. The species is named in honor of Mr. Edward Hoitt Nutter, who has rendered the writer much valuable assistance in the preparation of this paper. The type is from San Gregorio, San Mateo County, and is now in the collection of the department of geology, Stanford University. RANGE
Pliocene (lower). Purisima to Pescadero, San Mateo County (J. P. Smith, W. R. Hamilton, Arnold); Kreyenhagen's ranch, Fresno County (Watts).
Miocene (upper). Near Mount Hamilton, Santa Clara County (No. 5805, Cal. St. Min. Bur. Coll., collected by Mrs. A. E. Bush).» RALPH ARNOLD, 1906
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«Nanaochlamys nutteri (Arnold) ranges in age from late Miocene to Pleistocene occurring in unnamed Miocene outcrops on Mount Hamilton, Santa Clara County (Arnold, 1906), and from the Etchegoin (Nomland, 1917; Woodring and others, 1940), Purisima, San Joaquin (Adegoke, 1969), Merced (Arnold, 1906), and Rio Dell (Faustman, 1964) Formations in central and southern California (Moore, 1984). In the Purisima Formation it has been reported from Arnold’s (1908a) upper member exposed from Purisima to Pescadero Creeks (most abundantly in the sea cliff 0.5 mile south of the mouth of San Gregorio Creek) (Arnold, 1906, 1908a), from Purisima [Creek?] and the Sargent oil field area (Martin, 1916), in the Woodside Quadrangle (Mack, 1958; Mack in Esser, 1958), and at Pillar Point (Glen, 1959).»
POWELL II, C. L. 1998. The Purisima Formation and related rocks (upper Miocene - Pliocene), greater San Francisco Bay area, central California. Review of literature and USGS collection (now housed at the Museum of Paleontology, University of California, Berkeley). United States Geological Survey Open-file Report, 98-594, 102 p. [p. 64]
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«Comments.— This genus is here reported for the first time, outside of Japan, and is represented by the species Nanaochlamys nutteri. Chlamys islandica behringiana (Middendorf) of Grau (1959, pl. 23, fig. 2) and Chlamys (Chlamys) beringiana (Middendorf) of MacNeil (1967, pl. 23, fig. 3) also bear a marked resemblance to Nanaochlamys, and, to a lesser extent, so does Chlamys anapleus Woodring.
Grant and Gale ( 1931, p. 174) reported N. nutteri from the Pliocene of Japan, synonymizing Pecten heteroglyptus Yokoyama (1926, p. 304, pI. 33, figs. 1-6).» 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. B31]
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Nanaochlamys nutteri (Arnold); E. J. Moore, 1984, Tertiary Marine Pelecypods of California, plate 8, figures 4, 5.
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