Euvola keepi (Arnold, 1906)
ARNOLD, R. 1906. The Tertiary and Quaternary pectens of California. United States Geological Survey Professional Paper, 47: 1-264, pls. 1-53. [p. 60, pl. 5, fig. 1; pl. 6. figs. 1, 1a]
1906 Pecten (Pecten) keepi Arnold, 1906
R. Arnold, 1906, plates 5, 6.
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«Description. — Shell averaging about 75 millimeters in altitude, longer than high, plano-convex, equilateral, and with smooth margins: sides concave above; lateral area very broad. Right valve ventricose and ornamented by about 20 low, broad, rounded ribs, separated by shallow interspaces in which are low, broad intercalaries; the sulcation on the interior of the valve corresponding to the intercalary is often quite prominent; whole surface sculptured by inconspicuous incremental lines; hinge line more than one-half length of disk; ears equal, somewhat convex, rather obliquely truncated and turned up slightly at the corners; sculpture of ears consists of fine incremental lines; byssal notch rather small. Left valve flat, with a slight tendency toward concavity near the umbo, with broad lateral areas and with 18 or 19 low, rather flat-topped ribs; interspaces somewhat wider than the ribs; surface sculptured by line incremental lines; ears concave, obliquely truncated and sculptured by more or less irregular concentric lines.
Dimensions.— Alt. 75 mm.; hinge line to ventral margin 72 mm.; long. 82 mm.; hinge line 35 mm.; diameter 20 mm.; umbonal angle (left valve) 102°. This species is distinguishable from P. vogdesi and P. excavatus, which it resembles in general characteristics by its greater relative length, somewhat less convexity, greater umbonal angle, broader lateral areas and lower ribs. This species is found associated with P. carrizoensis and Ostrea vespertina in beds in the Carrizo Creek district which are probably of Miocene age. The type is from Alverson Canvon, San Diego County, and is now in the collection of Delos Arnold. Named in honor of Prof. Josiah Keep, of Mills College, whose works on California conchology have greatly stimulated the study of that subject on the Pacific coast. RANGE.
Miocene. Eight miles north of Mexican boundary, in Alverson Canyon, Carrizo Creek district. San Diego County (Bowers); Santa Rosalia, Lower California, west of and directly across the Gulf from Guaymas, Mexico (E. Palmer).»
RALPH ARNOLD, 1906
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«Comments.— The holotype is a double-valved specimen. The right valve is strongly convex and seems to have been inequilateral, with the posterior end the largest. This valve has about 17 very low, flat, almost obsolete wide ribs with narrow, slightly rounded interspaces. The auricles are smooth and strongly convex. The left valve is flat except near the umbos and ventral margin where it is concave. It has 15 narrow flat ribs separated by slightly wider interspaces, a few of which have one or two secondary riblets. The auricles are smooth and markedly concave. The right valve of E. refugioensis is smooth except on the umbo which has narrow, somewhat rounded, closely spaced ribs. The rest of the shell shows barely perceptible obsolete ribs a few ofwhich can be seen and felt as slight protuberances on the shell. The auricles are only slightly convex. The left valve of E. refugioensis has almost obsolete ribs which are wider and not as strongly demarcated as on E. keepi. The auricles are smooth and only slightly concave. All of these characters sérve to distinguish E. keepi from E. refugioensis, and I do not concur with Grant and Gale (1931, p. 229) that the species are the same.
Geographic range.— Southern California to Baja California Sur, and Santa Rosalia, Mexico. Geologic range.— Miocene(?) to Pliocene. Occurrence in the Californias.— Miocene: Isidro Formation (Stump, 1979); Miocene or Pliocene: Imperial Formation (Arnold, 1906; G D. Hanna, 1926a); Pliocene: Salada (Beal, 1948) and San Marcos (Durham, 1950) Formations.» 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. 70, 71]
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Euvola keepi (Arnold); E. J. Moore, 1984, Tertiary Marine Pelecypods of California: Propeamussidae and Pectinidae, plate 30, figures 5, 6.
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«RANGE: lower Pliocene, San Marcos and Imperial formations.
REMARKS: The ears of the left valve are more concave and more definitely set off than on P. refugioensis Hertlein; further, the apical angle is greater.» DURHAM, J. W. 1950. Megascopic paleontology and marine stratigraphy. In 1940 E. W. Scripps Cruise to the Gulf of California, Part II. Geological Society of America Memoir 43: 1-216, pls. 1-48. [p. 61]
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Pecten (Euvola) keepi Arnold; J. W. Durham, 1950, Megascopic paleontology and marine stratigraphy, plate 6, figures 5, 6.
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