540 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
OXOPLECIA COSTELLATA Cooper, new species 
Plate 138, B, figures 8, 9 
Shell of about medium size for the genus, wider than long and with sides 
rounded. Surface marked by closely crowded rounded costellae, 8 on the fold, 
7 in the sulcus, and 18 on the flanks. 
Pedicle valve gently convex in anterior and lateral profiles; sulcus broad and 
shallow ; tongue moderately long and broadly rounded ; flanks flattened and with 
gentle slopes to the sides. Brachial valve moderately convex in lateral profile and 
fairly strongly arched in anterior profile. Fold originating just posterior to the 
middle, moderately elevated and with costellae of the flanks crowded to its sides. 
Measurements in mm.—Holotype, length 10.1+, brachial length 9.1, midwidth 
12.3, hinge width 9.0, thickness 6.0. 
Type.—Holotype: 117126. 
Horizon and locality—Whistle Creek formation in Virginia: From a cut on 
U. S. Highway 60, 100 yards southeast of Whistle Creek, 2 miles northwest of 
Lexington, Lexington (15’) Quadrangle. 
Discussion.—This species is characterized by its flattish pedicle valve and 
closely crowded costellae. In these respects it suggests O. planiventra and 
O. recta. It differs from the former in having only 6 costellae on the fold and a 
much less convex brachial valve. It differs from the latter in having finer 
costellae. 
OXOPLECIA DEPRESSA Cooper, new species 
Plate 100, J, figures 44-49 
Shell small, transversely elliptical in outline and with rounded sides and gently 
rounded anterior margin. Anterior commissure moderately uniplicate. Surface 
marked by 9g costellae on the fold, 7 or 8 in the sulcus, and 16 costellae on the 
flanks; costellae rounded and crowded, often bifurcated or intercalated at the 
margin. 
Pedicle valve gently convex, most convex just anterior to the umbo; anterior 
profile broadly and faintly convex; umbonal region swollen; sulcus originating 
just posterior to the middle, shallow throughout and forming a short, broadly 
rounded tongue. Flanks bounding sulcus gently concave and with moderately 
sloping surface. Interarea short, apsacline. 
Brachial valve strongly convex in lateral profile and strongly domed in an- 
terior profile; umbonal and median regions strongly swollen; flanks moderately 
swollen and with steep sides. Fold inconspicuous, discernible only at the anterior 
and merged with the flanks and swollen median region. 
Measurements in mm.—Holotype, length 8.3, brachial length 7.7, midwidth 
10.5?, hinge width 6.8, thickness 5.3. 
Types.—Holotype: 117100b; unfigured paratype: 117100a. 
Horizon and locality.—Effna formation in Virginia: 4 miles southwest of 
Bland, Bland County. 
Discussion.—This species is unlike any other described herein in the modest 
