Chlamys etchegoini (Anderson, 1905)
ANDERSON, F. M. 1905. A stratigrafic study in the
Mount Diablo Range of California. Proceedings of the California Academy of
Sciences [3th Series], Geology, 2 (2): 155-248, pls. 13-35. [p. 198, pl. 18, figs. 92-93]
F. M. Anderson, 1905, plate 18.
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«Shell rather large, thick, and ovate in outline; ears nearly equal, costate; ribs strong and grouped in sets of 3 or 4, forming radial undulations in the shell, seen both within and without; margin of valve fluted within. The grouping of the ribs is a variable feature of the shell. In some specimens the depressions are wider, in others narrower than in the one figured. Concentric lines are usually visible on the shell.
Occurrence.— The species occurs with the two preceding in the Etchegoin Beds of the Kreyenhagen ranch on Zapata Chino Creek.» FRANK MARION ANDERSON, 1905
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«Swiftopecten parmeleei etchegoini (Anderson) has also been reported from the Purisima Formation by Glen (1959). This taxon occurs from northern California to Baja California Sur, Mexico in rocks from late Miocene to early Pleistocene in age (Moore, 1984). Its occurrence in the Purisima Formation at Moss Beach is based on two specimens - one incomplete collected by W. Glen and another far more complete specimen collected some years earlier by L. G. Hertlein (Glen, 1959) and from the Sargent oil field area (Martin, 1916 and Allen, 1945). The difference between this and the previous taxon is based solely on the presence of concentric swellings on the shell disk.»
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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«Comparison.— "This species can be distinguished from S. nutteri (Arnold), S. wattsi (Arnold), and S. parmeleei Dall by the absence of concentric swellings and the tendency for the major ribs to bifurcate at an earlier age than in the other species." (Adegoke, 1969, p. 105)
ChIamys parmeleei parmeleei has concentric swellings whereas C. parmeleei etchegoini does not. (Woodring, 1950, p. 83) Geographic range.— Northern California to Baja California Sur. Geologic range.— Miocene to Pleistocene. Occurrence in the Californias.— Miocene and Pliocene: Etchegoin Formation (Anderson, 1905; Arnold, 1906; Woodring and others, 1940); Pliocene: Almejas Formation (Hertlein and Grant, 1972), Cantil Costero (Hertlein and Allison, 1959), Careaga Sandstone (Woodring, 1950), Foxen Mudstone (Woodring, 1950), San Diego (Hertlein and Allison, 1959), and San Joaquin (Woodring and others, 1940; Adegoke, 1969) Formations; Pliocene and Pleistocene: Rio Dell Formation (Faustman, 1964).» 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. B60]
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Swiftopecten parmeleei etchegoini (Anderson); E. J. Moore, 1984, Tertiary Marine Pelecypods of California: Propeamussidae and Pectinidae, plate 22, figures 2, 3.
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«Remarks: – Chlamys cosibensis has hitherto been considered to be a synonym of Chlamys etchegoini (Anderson, 1905) or Chlamys nutteri (Arnold, 1906), both described from the Pliocene deposits of California, by several authors such as Grant and Gale (1931), Otuka (1935), Slodkewitsch (1938), Ilyina (1963) and Krishtofovich (1964). However, it is evident, as noticed from the description, that the present species is distinguishable from the Californian species by its smaller, inequivalved shell, larger posterior auricle, rather simple cardinal crura and characters of the radial ribs. In etchegoini the radial ribs of the right valve are six in number near the beak and they tend to become stout and elevated towards the ventral margin, and in the left valve the radial ribs are five in number near the beak and they tend to become stout and elevated towards the ventral margin. The radial ribs and their interspaces are sculptured with many fine intercalary threads which usually appear at the upper part of the shell.»
MASUDA, K. 1973. Chlamys cosibensis (Yokohama) of the Northern Pacific. Science Reports of the Tohoku University [2nd. Series - Geology], Special Volume, 6: 109-116, pls. 8, 9 [Hatai Memorial Volume]. [p. 112, 113]
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«Chlamys etchegoini (Anderson) is present in the Siphonalia zone (pl. 32, fig. 1) of the Etchegoin, and one small specimen (pl. 13, fig. 5) was found in the Pecten zone of the San Joaquin. This species is, however, abundant in the Pecten zone in the foothills farther west. C. etchegoini is closely related to the living Japanese C. swiftii (Bernardi). The Kettleman Hills specimens are very similar to C. swiftii, but they differ from 20 valves of that species available for comparison in having the ears more distinctly separated from the discs by angles that form furrows on the exterior of the valve. The difference is most marked on large specimens, particularly on left valves. It is not known whether all the American fossil forms can be separated from C. swiftii by this character. It is not well marked on the type of C. parmeleei (Dall), from the Pliocene at San Diego, possibly because it is a small specimen, but it seems likely that all the American forms will prove to be more closely related to C. parmeleei than to C. swiftii. C. parmeleei has prominent concentric swellings and is probably the same species as C. wattsi (Arnold), from the Coalinga district. Although the form with prominent concentric swellings may be a variation of C. etchegoini, it has not yet been found with that species in the Kettleman Hills. In the Kreyenhagen Hills this form occurs in the Jacalitos formation [29] as well as in the Pecten zone. Another Chlamys, C. cf. C. islandicus (Müller), is represented by fragments in the Acila zone. It is the last of the Pectinidae in the Kettleman Hills. (R. S.)»
[29] Nomland, J. O., Fauna from the lower Pliocene at Jacalitos Creek and Waltham Canyon, Fresno County, Calif.: California Univ., Dept. Geology Bull., vol. 9, pp. 203, 204, 1936.
WOODRING, W. P., R. STEWARD & R. W. RICHARDS. 1940. Geology of The Kettleman Hills oil field California. United States Geological Survey Professional Paper, 195: 1-170, pls. 1-57. [p. 91]
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Chlamys etchegoini (Anderson).; W. P. Woodring, R. Steward & R. W. Richards, 1940, Geology of The Kettleman Hills oil field California, plate 32, figure 1.
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