Propeamussium clallamensis (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. 57, pl. 3, figs. 1-3, 3a]
1906 Pecten (Propeamusium) [sic] clallamensis Arnold 1906
R. Arnold, 1906, plate 3.
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«Description.— Adult shell averaging about 10 millimeters in altitude, subcircular, equivalve, equilateral, thin, compressed, and with smooth margins. Right valve ornamented externally by numerous equally elevated, sharp, slightly imbricate, concentric lamellae, separated by equal interspaces, each of which is about five times as wide as the thickness of a lamella; hinge line somewhat longer than one-half length of disk; ears decidedly unequal, the anterior being about twice as long as the posterior; anterior ear arcuate in front and sculptured by numerous regular, sharp, elevated, concentric lamellae and 5 or 6 slightly elevated, unequally spaced radials; byssal notch not profound; posterior ear rectangularly truncated and ornamented with concentric sculpture similar to that of the anterior; interior of disk strengthened by nine strong, rounded, elevated, radiating ribs, which terminate abruptly at a length of 6 or 7 millimeters; the middle ribs are straight, but occasionally the lateral ones are faintly arcuate toward the middle rib. Left valve beautifully ornamented externally by numerous regular, thin, concentric, imbricating, prominently elevated lamellae which, sloping at an angle of about 45° toward the umbo, rise into 10 or 11 prominent, rounded; radiating pseudo-ribs, separated by somewhat wider interspaces, in nearly every one of which is an intercalated, imbricated pseudo-riblet; this riblet hegins only after the shell has attained a height of about 1.5 to 2 millimeters; ears similarly sculptured to those of the right valve.
Dimensions.— Alt. (type, left valve) 10 mm.; long. 9.5 mm.; hinge line 5.5 mm.; diameter about 0. 75 mm. This beautiful little Pecten appears to be allied to P. stanfordensis, but is easily distinguished from the latter by its beautifully lamellated surface, and in possessing 9 instead of 10 or more internal riblets. The type of P. clallamensis is a left valve (U. S. N. M. No. 164922) and was found at locality 4100, 1½ miles east of Pillar Point, near the mouth of the Pysht River, Clallam County, Wash., where it was associated with Aturia cf. ziczac Sowerby, Dolium petrosum Conrad, Fusus sp., Natica or Lunatia, Marginella or Erato sp., Nucula sp., Leda sp. (large, smooth), Tellina (Angulus) sp., Solemya sp., Dentalium substriatum Conrad. The cotype is a right valve (U. S. N. M. No. 164923), is from locality 4070, Bean Point, King County, Wash., and is associated there with Terebratula sp., Turritella sp., Marginella or Erato sp., Natica or Lunatia sp., Glycymeris sp., and Astyris sp. Both of the localities at which P. clallamensis have so far been found are in the lower portion of the Oligocene-Miocene series. RANGE
Oligocene-Miocene. Mouth of Pysht River, Clallam County, and Bean Point, west of Seattle, King County, Wash. (Arnold).»
RALPH ARNOLD, 1906
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«Observations. As pointed out by Arnold, this species is similar to P. stanfordensis but may be distinguished from it in having 9 instead of 10 ribs and in the lamellated character of its surface.
Holotype. (U.S.N.M. 164922.) Figured in the present report, pl. 17, figs. 3, 6.
Geologic range. Upper Oligocene. Geographic distribution. Northern side of Olympic Peninsula, Washington. Type locality. Locality (U.W. 681.) In sea cliffs one-half mile east of Pillar Point, Clallam County, Washington.» WEAVER, C. E. 1943. Paleontology of the marine Tertiary formations of Oregon and Washington. University of Washington Publications in Geology, Volume. 5 [1942], (parts 1-3), p. 1-789, pls. 1-104. [p. 95]
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Pecten (Propeamussium) clallamensis Arnold; C. E. Weaver, 1943, Paleontology of the marine Tertiary formations of Oregon and Washington, plate 17, figures 3, 6.
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