Euvola slevini (Dall & Ochsner, 1928)
DALL, W. H. & W. H. OCHSNER. 1928. Tertiary and Pleistocene Mollusca from the Galapagos Islands. Proceedings of the California Academy of Sciences, 17 (4): 89-139, pls. 2-7. [p. 118, pl. 3, fig. 9; pl. 4, fig. 4]
1928 Pecten (Pecten) slevini Dall & Ochsner, 1928
W. H. Dall & W. H. Ochsner, 1928, plates 3, 4.
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«Shell large, right valve inflated, left valve flattish, medially somewhat concave; hinge-line short, overhanging that of the left valve; posterior ear arched, with low concentric lamellation, and two or three feeble indications of radial ridges; anterior ear flatter with closely crowded lamellae and four or five rather strong radial riblets ; this ear is separated by a deep groove from the disk; the ctenolium, if any, is defective in the specimens; right valve with 17 prominent rounded ribs, with wider, not channelled, interspaces; the posterior submargin is narrow, with two or three feeble radial riblets; the whole surface is over run with undulate equal and equally spaced low fine concentric lamellae with about equal interspaces; the left valve has 15 ribs with similar sculpture and similar posterior submargin; hinge-plate with a large deep resiliary pit and in the right valve three anterior and two (?) posterior, strongly cross-striated radial ridges of which the dorsal is the longer; basal margin defective, but internally grooved. Estimated height, 70 mm.; width, 80 mm.; maximum diameter, 26 mm.; length of hingeline, 39 mm.
Holotype: No. 2944; paratype: No. 2945, Mus. Calif. Acad. Sci., collected by W. H. Ochsner and Joseph R. Slevin, November 17, 1905, from upper horizon (zone D), on east shore of Indefatigable Island, Galapagos Group. Probably Pliocene. This species is quite close to the Pliocene P. hemphillii Dall, from Pacific Beach near San Diego, California; but apparently not so near any of the typical Pectens of the Panama region. The species is named for Mr. Joseph R. Slevin, a member of the expedition of 1905-1906.» WILLIAM HEALEY DALL & WASHINGTON HENRY OCHSNER, 1928
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«Node 9 (Fig. 7) marks the beginning of the Galápagos-Cocos clade containing the extinct species E. slevini (Fig. 8.1–8.7) and the derivative extant species E. galapagensis (Figs. 6.1–6.6, 8.10) and E. hancocki (Fig. 6.7–6.12). Euvola slevini differs from E. heimi in having extremely acute posterior auricles and a somewhat reduced number of ribs on its right disk (19, compared to 20 or 21 in E. heimi). The three species of the Galápagos-Cocos clade are plesiomorphic in lacking medial riblets on the left valve and hypertrophied left auricular costae, and thus are set apart from the Californian E. coalingaensis-vogdesi lineage. The age of E. slevini was regarded by Dall and Ochsner (1928, p. 118) as ‘‘probably Pliocene.’’ Another specimen of E. slevini (Fig. 8.1–8.4) was collected by J. Lipps and C. Hickman of the University of California Museum of Paleontology from what they believe to be the same locality on Isla Santa Cruz collected by Ochsner in 1905–1906 (Hickman and Lipps, 1990). Hickman and Lipps (1985) did not find any rocks older than Pliocene on this island.»
WALLER, T. R. 2007. The evolutionary and geographic origins on the endemic Pectinidae (Mollusca: Bivalvia) of the Galapagos Islands. Journal of Paleontology, 81 (5): 929–950, figs. 1-9. [p. 941]
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Euvola slevini (Dall and Oschner, 1928); T. R. Waller, 2007, The evolutionary and geographic origins on the endemic Pectinidae of the Galapagos, figures 8.1-8.7
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