Argopecten abietis abbotti (Hertlein & Grant, 1972)
HERTLEIN, L.G. & U.S. GRANT IV. 1972. The Geology and Paleontology of the marine Pliocene of San Diego, California (Paleontology: Pelecypoda). Memoirs of the San Diego Society of Natural History. Memoir 2, Part 2b. pp. 143-409, pls. 27-57. [p. 196, pl. 34, fig. 5; pl. 36, figs. 1, 6]
1972 Chlamys (Argopecten) abietis abbotti Hertlein & Grant, 1972
L. G. Hertlein and U. S. Grant IV, 1972, plates 34, 36.
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«Type specimen.— Holotype in the type collection of the San Diego Society of Natural History.
Type locality.— From cut in exposure at Frontier Housing Project, Loma Portal, San Diego, California; Patrick Hanratty collector, April, 1945. Additional localities in San Diego Fm. — C.A.S. L.A.M. 302A, P.87: No. 8325. S.D. 409. Description.— Shell large, thick, both valves highly convex, somewhat elongated posteriorly; hinge Une long, a little over two thirds the length of the valves. Right valve with 21 radial ribs which are high, narrowly flattopped and steeply sloping until the valve is about 70 mm high, then becoming lower and broadly rounded; the sides of the ribs and the interspaces are ornamented with close-set fringing lamellae; anterior ear sculptured with 4 or 5 fine radial riblets, a well developed byssal notch present; posterior ear faintly radially striated and with lines of growth which reveal a shallow sinuation. Left valve with ribbing similar to that of the right except that the ribs are narrower and more triangular, the anterior ear with a shallower notch and with faint traces of fine riblets. Inner margin of valves scalloped by the corresponding ribs and interspaces on the exterior. Dimensions: length 129.0 mm, height 118.0 mm, convexity (both valves together), 64.0 mm, length of hinge line 88.0 mm. Remarks.— The shell characters of this new subspecies appear to be intermediate between those of Chlamys (Argopecten) abietis E. K. Jordan and Hertlein (368) and those of C. (A.) circularis aequisulcata Carpenter (369). This new subspecies differs from C. (A.) abietis in the deeper notch under the right anterior ear, in the more widely spaced ribs and by the more flattened character of the ribs toward the ventral.margin of the left valve. It differs from C. (A.) circularis aequisulcata in the larger, thicker shell, longer hinge line, more triangular shape of the ribs in the early stages of growth but which become rounded and flattened toward the ventral margin on the right valve, and also in the more highly convex left valve with narrower interspaces between the ribs. The rotund appearance of large specimens of this new subspecies lends a general resemblance to C. (A.) hakei Hertlein but it may be separated from that species by the fewer ribs (21 or 22 rather than 24 to 27) which are triangular until the shell is about 70 mm high and then become broader and flatter toward the ventral margin. A large, thick, left valve in the collections of the Los Angeles County Museum, collected by Charles Sternberg at 32nd Avenue and Woolman Street, San Diego, is 105 mm long, 96 mm high, the convexity about 27 mm. It is sculptured with 21 ribs. The interior is reddish-brown in color especially the ventral half of the valve. The shell is partially covered with hard, gray, fine grained sandstone. Small oysters are attached to the exterior of the valve as might occur if the empty shell lay upon the sea bottom for a time before it was covered with sediment. The very large size of this valve and the traces of coloration on the interior are similar to those of C. (A.) c. aequisulcata Carpenter but the size and thickness correspond more with those of C. (A.) abietis abbotti and we refer it provisionally to this subspecies. Two specimens from Loc. 595 (UCLA), about two miles north of Somis, Ventura Co., California, in a Pecten reef apparently near the base of the Long Canyon Member of the Las Posas Formation, of late Pliocene age, are quite similar to the type specimen of C. (A.) abietis abbotti but the ribs are slightly broader. The larger specimen is 141.5 mm long, 132.6 mm high, the convexity (both valves together), 61 mm. A smaller specimen collected with the two large fossils from Ventura County, is 74 mm long, 69.6 mm high, the convexity (both valves together), 34 mm. The ribs on this specimen, especially on the left valve, are triangular with fringing lamellae, corresponding in every way with typical C. (A.) abietis of the same size from Lower California. This subspecies is named for Clinton G. Abbott, former Director of the Museum of the San Diego Society of Natural History, whose encouragement to the authors during the preparation of the early portion of this memoir is greatly appreciated». LEO GEORGE HERTLEIN & ULYSSES SIMPSON GRANT IV, 1972
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