Neithea duplicicosta (C. F. Roemer, 1849)
ROEMER, C. F. 1849. Texas, Mit besonderer Rueeksicht auf deutsche Auswanderung und die physischen Verhaeltnisse des Landes. Bonn [p. 398]
1849 Pecten duplicicosta Roemer, 1849
Pecten duplicicosta n. sp.; C. F. Roemer, 1852, Die Kreidebildungen von Texas, plate 8, figures 2a, 2b.
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«20. Pecten duplicicosta n. sp. Valva maiore 2" 2"' lata, 1" 11"' longa, gibbosa et suborbiculari; iugis radiantibus 5, crassis, prominentibus, instructa costis radiantibus et iugorum intervalla et iuga ornantibus.
Diese zur Abtheilung der Neitheen (Ianira Schumacher bei d'Orbigny) gehörige Art, ist durch die starken, wulstförmigen, radialen Rippen, welche, so wie ihre Zwischenräume, von kleineren Rippen bedeckt werden, ausgezeichnet. Das einzige vorliegende unvollständige Exemplar der größeren Klappe wurde am oberen kaufe des Pedernales gefunden, janira Fleuriausiana d'Orbigny l. c. lll. Pl. 443. hat ähnliche gerippte Wülste, aber die Rippen oder Falten zwischen den Wülsten sind zahl reicher, und die Schaale ist gewölbter, als bei der teranischen Art.» CARL FERDINAND ROEMER, 1849
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«Shell rather large, subcircular in outline, very inequivalve, the right valve strongly arched, the left valve slightly concave; surface of the right valve marked by 6 broad, subangular, principal ribs that produce slight angulations on the ventral margin, and by numerous subequal subordinate ribs, of which there are about 3 on each of the principal ribs and 2 in each interspace, all crossed by numerous, regular, fine, concentric lines. No perfectly preserved left valve has been seen, but from molds and fragments it is evident that the sculpture is similar to that of the right valve except that the principal ribs are much less strongly marked. The ears are triangular, subequal, and inconspicuous in the adult, but in a young right valve (pl. 89. fig. 2) they are relatively large, and the anterior one is rounded and shows a distinct byssal notch.
A medium-sized specimen measures 60 mm. in height, 65 mm. in length, and about 25 mm. in convexity; umbonal angle 110° to 120°. Some specimens from near the head of Frio River show sculpture variously disguised according to the state of preservation. The most common change is a reduction in the size and angularity of the principal ribs between which there are 3 subordinate ribs in each interspace, giving the shell the appearance of a distinct species, but this change is caused by a combination of internal and external features due to the accidents of fossilization. The sculpture of this species somewhat resembles that of Pecten roemeri Hill (1889, p. .8), and the opinion has been expressed that the two might be identical. A comparison of specimens shows that they are not even closely related, P. roemeri being a much larger and almost equivalved form. Plesiotypes: U.S.N.M. 103225, 103226. Locality and position: The species is not very common and appears to be restricted to the Edwards limestone. Roemer's type came from the upper course of Pedernales River, and Cragin's specimens from South Mountain, Gillespie County, Tex. The smaller of the specimens here figured is from the southern end of the Quitman Mountains in Hudspeth County, and the larger one from the Edwards Plateau near the head of Frio River in Edwards County where the species is common. The Geological Survey collections also contain specimens from Kickapoo Springs at the head of the west fork of Nueces River in Edwards County, from a locality near Belton in Bell County, and from Bluff Creek 5 miles from Crawford in McLennan County, Tex.» STANTON, T. W. 1947. Studies of some Comanche pelecypods and gastropods. United States Geological Survey Professional Paper, 211: 1-256, pls. 1-67. [p. 43]
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Pecten (Neithea) duplicicosta Roemer; T. W. Stanton, 1947, Studies of some Comanche pelecypods and gastropods, plate 39, figures 1, 2.
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