Propeamussium waylandi (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. 58, pl. 3, figs. 4-5]
1906 Pecten (Propeamusium) [sic] waylandi Arnold, 1906
R. Arnold, 1906, plate 3.
|
«Description.— Adult shell averaging about 9.5 millimeters in altitude, somewhat longer than high, subcircular, equivalve, equilateral, thin, somewhat convex in youth, but becoming more compressed with age; margins smooth. Disk of right valve sculptured by numerous fine lines of growth and numerous, more or less obsolete, fine radiating lines; hinge line equal to about one-half the length of the disk; ears subequal; anterior arcuate in front and faintly sculptured concentrically by sharp lines and radially by faint ridges; byssal notch narrow and shallow; posterior ear slightly obliquely truncated and sculptured by faint radial ridges and fine, sharp, concentric lines; interior of disk strengthened by 8 subequal, strong, narrow, smooth, convex-topped riblets, which are widely separated and which terminate abruptly at about 6 to 8 millimeters from the umbo; these internal riblets are usually straight, but the ones distant from the center are often slightly arcuate toward the center. Left valve, up to an altitude of 6 or 8 millimeters, ornamented by 8 more or less prominently elevated, narrow, convex-topped radiating ridges, corresponding with the same number of equally long, smooth, convex-topped internal riblets; whole surface of disk sculptured by numerous subequal, inequidistant, sharp, radiating lines (usually varying from 5 to 7 between each major ridge) and faint incremental lines, the latter becoming prominent as the radiating ridges become obsolete; ears similar to those of right valve, with the exception that there is no byssal notch in the anterior one.
Dimensions.— Alt. 9.5 mm.; long. 12 mm.; hinge line 5.5 mm.; diameter about 0. 75 mm. This little Pecten is closely allied to P. stanfordensis, but may be distinguished from the latter by the more prominently elevated ridges on the left valve, the greater prominence of its microscopic radial sculpture, and the smaller number (8 instead of 10 to 12) of internal riblets. P. waylandi is distinguishable from P. clallamensis, with which it is associated, by its relatively longer disk, simple and less prominent external sculpture, and fewer (8 instead of 9) internal riblets. It is allied to P. interradiatus Gabb, but is much smaller, being only about one-half as large, has a much shorter hinge line, and its left valve is much more strongly sculptured; it also occurs in a horizon probably later than that in which P. interradiatus is found. The type of P. waylandi (U.S.N.M., No. 164924) was found with the type of P. clallamensis at locality 4100, 1½ miles east of Pillar Point, near the mouth of the Pysht River, Clallam County, Wash., and a list of its associated species is given in the discussion under P. clallamensis. The cotype of P. waylondi (U.S.N.M., No. 164925), a mold of the interior of a right valve, was found at locality 4115, 2½ miles west of Gettysburg, Clallam County, Wash., where it was associated with Fusus sp., Leda sp., Macoma or Tellina sp., and Aturia cf. ziczac Sowerby. The faunas associated with P. waylandi, at both of the localities where it has so far been found, indicate the lower portion of the widely distributed Oligocene-Miocene series. The species is named in honor of Mr. Russell G. Wayland, of Seattle, Wash. , who assisted the writer during part of his paleontological reconnaissance trip along the northwestern coast of Washington in the summer of 1904. RANGE
Oligocene-Miocene, 2½ miles west of Gettysburg, and 1½ miles east of Pillar Point, near the mouth of the Pysht River, Clallam County, Wash. (Arnold).
RALPH ARNOLD, 1906
|