UT6919 and



Pecten siederensis

The dimensions of these shells are generally 23.5mm x 22mm.  The shell is medium to large, subequilateral, practically equivalve, compressed, and  suborbicular.  The postero-dorsal margin is decidedly concave, the antero-dorsal is more nearly straight and umbos sharp.  The ears are practically the same size; the hinge line is straight and relatively short.  The right valve is slightly convex and extremely thin to the point of being almost transparent.  The anterior ear is a big longer than the posterior ear and its far border is gently rounded.  The left valve is similar to the right, has almost equal ears, and the outer angle of the the anterior is acute, whereas that of the posterior is obtuse.  This species was found in the upper division of the Buda Limestone, Sieder Springs, Austin, Texas.