Vertipecten lachenbruchi MacNeil, 1967
MACNEIL, F. S. 1967. Cenozoic pectinids of Alaska, Iceland, and other nothern regions. United States Geological Survey Professional Paper, 553: 1-57, pls. 1-25. [p. 39, pl. 1, figs. 3-8; pl. 2, figs. 4, 7]
1967 Vertipecten lachenbruchi MacNeil, 1967
F. S. MacNeil, 1967, plates 1, 2.
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«Description.— Shell of medium size and moderately inflated, the left valve more inflated than the right, valve; beaks moderately sharp; dorsal margins weakly concave; hinge line moderately long and straight. Ears prominent and moderately broad; anterior ear of right valve moderately broad with a broad strongly sculptured byssal area, byssal notch broad but moderately shallow; posterior ear of right valve moderately long with a concave moderately sloping posterior margin; anterior ear of left valve with a weakly concave but nearly vertical anterior margin; posterior ear of left valve moderately short and strongly sloping along its posterior margin. Sculpture consisting of moderately small and closely set ribs that are variable in shape and spacing and ornamented with beadlike to scabrous projections; left valve (holotype) with a maximum of 47 ribs, of which about 20 might be considered primaries, the secondaries are variable in size and in the number between pairs of primaries; right valve ribs sharper and irregularly paired, especially near the beaks, scabrous to bluntly spined; ears strongly sculptured with primary and secondary riblets, growth lines on byssal area strongly raised and irregular.
Discussion.— This species is based on specimens from two localities, the holotype, a left valve and the largest specimen, from McGinty Point on the mainland, and several scraps of right valves from Unga Island. Acila shumardi occurs at both localities. I cannot say on the basis of the material at hand whether this species is very close to any others described. Its sculpture resembles that of Pecten (Chlamys) proavus Arnold (1906, p. 52, pl. 2, figs. 6-8) from a locality between Pescadero Creek and the San Lorenzo River, San Mateo County, Calif. Arnold thought its age was Eocene, but Keen and Bentson (1944, p. 93) said "Oligocene or Miocene." Earl Brabb, of the U.S. Geological Survey (oral commun., June 8, 1964) thought the horizon of P. proavus was within the Zemorrian foraminiferal stage. V. lachenbruchi may be fairly closely related to Pecten (Chlamys) grunskyi Hertlein (Pecten branneri, Dickerson, 1917, pl. 28, fig. 2) from which it differs mainly by having weak spines or scales on its ribs. The ears of the right valve are very similar on the two species. Types: The holotype (USNM 645031), an incomplete left valve, has a length of 58 mm and if complete probably would be about 80 mm. Three para types (USNM 645032, 645033, 645034) are smaller fragmental right valves. Two figured scraps are numbered USNM 645035 and 645036. Type locality: An unnamed formation within and possibly near the top of the Acila, slmmardi zone (middle Oligocene), east tributary to Mud Bay, south of Port Moller, Alaska Peninsula, USKJS M1025. Other occurrences: Paratypes and figured specimens are from an unnamed formation south of West Head, northeastern Unga Island, Alaska, probably the same stratigraphic horizon as the type locality near Mud Bay, USGS 5037.» FRANCIS STEARNS MACNEIL, 1967
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