40 Palaeontographica Americana 40 



Scapharca (Scapharca) staminca Dall, Wagner Free Inst. Sci., Trans., vol. 3, pt. 4, pp. 642, 657, 658, 



1898. 

 Area (Scapharca) stauiivea Glenn, Maryland Geol. Surv., Miocene, pp. 386, 3S7, 390, pi. 105, figs. 



2-6, 1904. 



"Shell thick, prominently convex; with about twenty-eight ribs which are rounded 

 and narrower than the intervening spaces, excepting on the anterior side, where they are 

 broader, and simply wrinkled, those of the anterior part of the disk ha-\-e one or two 

 longitudinal impressed lines; they are crossed by numerous transverse, elevated lines, 

 which are hardly more distant from each other than their own width; intervening spaces 

 wrinkled: beaks distant, curved a little backward, and the tip a little behind the middle 

 of the hinge margin: area flattened, a little curved, rather spacious, with obvious im- 

 pressed, oblique lines: hinge 7nargin rectilinear, with small, numerous teeth: posterior 

 margin regularly arcuated: base subrectilinear, very deeply crenated.' anterior margin 

 oblique, rectilinear: anterior side abruptly compressed * * *. 



"It seems to be related to some of the varieties of A. granosa, L.; but the 

 ribs are more slender; the apex is curved a little backward, &c." — Say, 1832. 



In Say's description posterior and anterior are interchanged. Anterior part of 

 the shell inflated, posterior sharply flattened, forming almost a right angle with the rest 

 of the shell; between the anterior inflation and umbonal ridge the shell is flattened and 

 often shows a wide, shallow sulcus which increases toward the ventral margin ; outline 

 rhomboidal, anterior margin rounded, basal nearly straight and parallel to the hinge-line 

 or somewhat sinuate posteriorly, posterior margin nearly straight, forming a sharp angle 

 with the hinge-line and almost a right angle with the ventral margin; ribs twenty-six to 

 thirty, commonly about twenty-seven; anterior ribs often divided by a shallow sulcus, 

 ribs about the iimbonal ridge often with two or m"ore longitudinal sulci producing a stri- 

 ated appearance; ligament area wide, with five or six concentric furrows usually; teeth 

 often irregular at both ends of the hinge. 



It is apparent that Conrad's A. elevata is the same as A. staminca Say. Glenn 

 (Marvland Geol. Surv., Miocene, p. 388), says, "A careful comparison of what are doubt- 

 less the type specimens of A. calliplcura shows that it is but a short, elevated, thickened 

 and well sculptured form of A. staminca^ ^. //v'^raf/z-a Conrad is a short, high and 

 little sculptured form of A. statninea. Short, high specimens of the species are not un- 

 common. A long, rounded, well- sculptured variety of A. staminca approaches A. ic/onea 

 closely. 



Dimetisions. — Lon.-fi6,-32; alt. -|- 11,-30; diam. 44 mm. 



Occurrence. — Miocene of Calvert Cliffs, Choptank River and Jones's Wharf, near 

 Centreville, Maryland; of York River, Virginia, and Walton County, Florida. — Dall. 

 Choptank Miocene of Governor Run, two miles south of Governor Run, Flag Pond, 

 Jones Wharf, Cuckold Creek, Turner, Dover Bridge, Peach BloSsom Creek, Greensboro, 

 Marj^land. — Glenn. Miocene of Choptank River, Governor Run and Patuxent River, 

 Maryland. — C. U. Musextm. 



