Chlamys (Plagioctenium) gonioides Woodring, 1925
WOODRING, W. P. 1925. Miocene mollusks from Bowden, Jamaica. Pelecypods and scaphopods. Carnegie Institution of Washington Publication 366: 222 p., pls. 1-28. [p. 71, pl. 8, figs. 11, 12]
«Chlamys (Plagioctenium) gonioides, new species.
(Plate 8, Figures 11, 12.) The folowing is a description of this species:
Shell small, subequivalve, suborbicular, posterior end slightly more extended and unevenly rounded; posterior dorsal margin longer than anterior; right valve sculptured with 22 or 23 subangular radial ribs, their summit slightly rounded, on adult shells the ribs are rounded at the ventral margin, ribs separated by subangular interspaces; on the slope of ribs and in bottom of interspaces are fine, closely spaced concentric lamellae, usually not rising above summits of ribs; left valve sculptured with 18 or 19 similar but broader and more sharply angular ribs and similar concentric lamellae; submargins of both valves smooth, except for fine, inconspicuous concentric lamellae; auricles subequal, sculptured with 4 or 5 narrow, unequally spaced radial ribs crossed by concentric lamellae; cardinal crura large. A left valve: length 14 mm.; height 14.1 mm.; diameter 3.2 mm.; length of hinge 8.2 mm. A right valve: length 12.3 mm.; height 12.2 mm.; diameter 3 mm.; length of hinge 6 mm. The two valves are almost equally inflated, but most left valves are slightly less inflated and more inequilateral. The radial sculpture on the two valves is quite different; on the left valve the ribs are fewer, broader, and more distinctly angular, though slightly rounded especially at the ventral margin and in the umbonal region. The concentric lamellae rarely override the ribs. Two large right valves, larger than the holotype, have ribs that are rounded and even flattened at the ventral margin. As usual, young shells are more rounded than adults. C. gonioides closely resembles C. oxygonum described by Sowerby from the Dominican Republic. The U. S. Geological Survey expedition collected from the Cercado formation on Rio Mao (station 8521) a valve that agrees with Sowerby's description. The Bowden species has less angular ribs and interspaces, shallower interspaces, and weaker concentric sculpture. Type material.— Holotype (left valve, U. S. Nat. Mus. No. 352787); paratype (right valve, U. S. Nat. Mus. No. 353076).» WENDELL PHILLIPS WOODRING, 1925
|
W. P. Woodring, 1925, plate 8.
|