Chlamys cornwalli (Clark & Arnold, 1923)
CLARK, B. L. & R. ARNOLD. 1923. Fauna of the Sooke Formation, Vancouver Island. University of California Publications, Bulletin of the Department of Geological Sciences, 14 (5): 123-234, pls. 15-42. [p. 140, pl. 25, figs. 1, 4, 5]
1923 Pecten (Chlamys) cornwalli Clark & Arnold, 1923
B. L. Clark & R. Arnold, 1923,
plate 25. |
«Type.— No. 30059, Univ. Calif. CoIl. Invert. Pal.; L. S. J. U. locality N. P. 129.
Cotype.— No. 30058, Univ. Calif. CoIl. Invert. Pal.; L. S. J. U. locality N. P. 129. Cotype.— No. 30231 Univ. Calif. CoIl. Invert. Pal.; I. E. Cornwall locality A. Shell somewhat variable in outline and sculpturing, nearly equilateral; height considerably greater than length; subequivalved; apical angle between 85 and 90 degrees. Dorsal edges straight or neal'ly so; the posterior edge slightly longer than anterior; dorsal margins rather strongly depressed. Left valve sculptured by 20 to 21 rounded, radial ribs, some of which may be twice as wide as the others; interspaces between ribs also variable, some being wider than tops of ribs, others narrowel'. There appears to be no system in width and spacing of ribs, which is more regular on some specimens than on others. Radial ribbing does not extend on to depressed dorsal margins. Surface also covered by rather coarse imbricated concentric lines of growth. Ears equal, with anterior and posterior edges straight; anterior ear sculptured by about eight rather obscure moderately fine radiating ribs; at least five or six of these ribs on posterior ear. Right valve sculptured by about twenty-one rounded radial ribs with interspaces averaging about width of ribs; ribbing somewhat narrower near dorsal margins, but taken as a whole much more regular than that of left valve; surface as a whole sculptured by heavy imbricating lines of growth. Ears unequal; anterior ear longer with a broad fairly deep byssal notch; four ctenidial teeth visible in notch, and five in filled area back of notch on cotype. l<'our radial ribs on anterior ear; apparently five or six radial ribs on posterior ear but on specimens at hand almost obsolete. Ligamental pit deep; teeth absent. Dimensions of type (a left valve): Length, 47 mm.; height, 52 mm.; length of anterior dorsal margin, 29 mm.; length of posterior dorsal margin, 34 mm. Dimensions of cotype No. 30231 Univ. Calif. CoIl. Invert. Pal. (a right valve): Length, 55 mm.; height, 62.5 mm.; length of posterior dorsal margin, 37 mm.; length of anterior dorsal margin, about 33 mm. Occurrence.— Leland Stanford Jr. University locality N. P. 129; I. E. Cornwall locality A. Named in honor of Mr. Ira E. Cornwall of Victoria, British Columbia.» BRUCE LAWRENCE CLARK & RALPH ARNOLD, 1923
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«Pectinids from the Juanian Stage (late Oligocene) include Leochlamys columbianum (Clark and Arnold) and Chlamys cornwalli (Clark and Arnold), both from the Sooke Formation of the southwest coast of Vancouver Island, British Columbia. An incomplete specimen of Leptopecten is known from the upper part of the Twin River Formation, northern Olympic Peninsula, Washington (Addicott, 1976b). A small Chlamys from an unnamed marine tuff and sandstone unit near Scotts Mills (Peck and others, 1964), about 50 km south of Portland, Oregon, has been variously identified as Pecten sespeensis (Arnold) (Durham and others, 1942) and Chlamys aff. C. columbianum (Clark and Arnold) (Vokes in Peck and others, 1964). This pectinid (PI. 1, figs. 3, 5) is here regarded as an undescribed species of Chlamys; it is represented in collections from two USGS localities (21347 and M2037). It occurs with Bruclarkia acuminata (Anderson and Martin) and Liracassis cf. L. apta (Tegland) in the collection from USGS locality 21347 (Vokes in Peck and others, 1964).
The peak in taxonomic diversity registered during the Juanian Stage (fig. 1) is an indication of the occurrence of both shallow and moderately deep to deep-water facies, each with its distinctive pectinid associations. In addition to the species listed above, five species of mud pectens are described or recorded from this stage.» ADDICOTT, W. O. 1981. Significance of pectinids in Tertiary biochronology of the Pacific Northwest. Geological Society of America, Special Papers, 184: 17-38, pls. 1-4. [p. 23]
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Chlamys cornwalli (Clark and Arnold); W. O. Addicott, 1981, Significance of pectinids in Tertiary biochronology of the Pacific Northwest, plate 1, figure 2.
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