Chagrepecten dallasi (Jordan & Hertlein, 1926)
JORDAN, E. K. & L. G. HERTLEIN. 1926. Expedition to the Revillagigedo Islands, Mexico, in 1925, IV. A Pliocene Fauna from María Madre Island, Mexico. Proceedings of the California Academy of Sciences, Fourth Series, 15 (4): 209-217. [p. 213, pl. 23, figs. 2, 5, 6, 8]
1926 Pecten (Chlamys) dallasi Jordan & Hertlein, 1926
E. K. Jordan & L. G. Hertlein, 1926, plate 23.
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«Shell of medium size, moderately thick, in several specimens with strong lines of restricted growth; valves mildly arched, and slightly extended posteriorly; hinge line a little over half the total length of the disk. Right valve ornamented by about 15 to 19 almost flat-topped radiating ribs, separated by slightly rounded interspaces almost as wide as the ribs, the summit of the ribs smooth, the sides and interspaces sculptured by fine, sharp, subequal radiating ridges and grooves, the shoulder of each rib on either side marked by a deeper groove; anterior dorsal and posterior dorsal areas of disk smooth; ears unequal, the anterior with a well developed byssal notch and sculpture consisting of about six radiating riblets crossed by concentric lines of growth; posterior ear obliquely truncated behind, and ornamented by four or five radiating riblets between which the interspaces bear fine incised radiating lines. Left valve sculptured much as right; anterior dorsal and posterior dorsal margins of disk sloping more abruptly to base of ears than on right valve: anterior ear indented by a rounded byssal notch and ornamented by five radiating riblets between which are minute sharp radiating grooves; posterior ear obliquely truncated and sculptured much as anterior, the radiating riblets. however, much more subdued and less prominent. Height 42 mm.; length 43 mm.; diameter 13 mm.; apical angle approximately 105°.
Type: No. 1862, paratypes Nos. 2072, 2073, 2074, 2075, 2076, and 2077, Mus. Calif. Acad. Sci., from Loc. 795 (C.A.S. coll.), Cañons one or two miles from San Antonio Point, east coast of Lower California; upper Pliocene; Fred Baker collector; also No. 2078, Mus. Calif. Acad. Sci., from Loc. 937 (C.A.S. coll.), Arroyo Hondo, Maria Madre Island, Mexico; upper Pliocene; G. Dallas Hanna and Eric K. Jordan collectors. Pecten dallasi is easily recognized by the peculiar minor radiating sculpture superimposed on the major ribs and interspaces. The number of ribs varies considerably, as does the obliquity of the valves. This species is abundant in the upper Pliocene of the Gulf of California region, and, as we have specimens from there in better state of preservation than those from Maria Madre Island, the type is selected out of a lot from Lower California. The collection from Maria Madre contains three specimens of the species. The writers wish to express their obligation to Dr. Fred Baker, who collected the type specimen. The species is named in honor of Dr. G. Dallas Hanna, whose work on the Pliocene of Imperial County, California, and on Lower California has added to our knowledge of the region.» ERIC KNIGHT JORDAN & LEO GEORGE HERTLEIN, 1926
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«In the present study, Pecten cactaceus, Chagrepecten paracactaceus n. gen., n. sp. from the Pliocene upper Gurabo and Mao formations of the Dominican Republic, and Pecten (Chlamys) dallasi Jordan & Hertlein, 1926, from the middle Pliocene of Baja California Sur, Mexico, are brought together into the new genus Chagrepecten. Although these species have the vesiculate sculpture present in Cryptopecten, they differ from species in that genus in the characters pointed out by Hayami (1984: 90).»
WALLER, T. R. 2011. Neogene Paleontology of the Northern Dominican Republic. 24. Propeamussiidae and Pectinidae (Mollusca: Bivalvia: Pectinoidea) of the Cibao Valley. Bulletins of American Paleontology, 381: 1-197 [p. 67]
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«RANGE: middle Pliocene, Carmen formation.
REMARKS: Only three specimens were found in the collections.» 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. 65]
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Chlamys dallasi (Jordan and Hertlein); J. W. Durham, 1950, Megascopic paleontology and marine stratigraphy, plate 6, figure 2.
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