390 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
slightly emarginate. Surface of the pedicle valve marked medially by a strong, 
narrow costa extending from the beak to the anterior margin and on each side 
is intercalated a small costa. Median costa generally elevated above those sur- 
rounding it, and the area occupied by the 2 or 3 neighboring costae is flattened. 
Surface on each side of median costa marked by about 8 costae. Brachial valve 
marked medianly by a deep sulcus extending from near the beak to the front 
margin. Sulcus broadly V-shaped in section and occupied by 4 or 5 costae. 
Pedicle valve hemiconical, with nearly flat lateral profile and slightly pro- 
tuberant beak; anterior profile broadly but gently convex. Lateral slopes flat- 
tened and moderately steeply inclined. Interarea catacline. Muscle field short, 
not strongly thickened. Dental plates very short, receding. Apical plate only 
slightly developed. 
Brachial valve moderately convex in lateral profile with the greatest curvature 
at the umbo; anterior profile bilobed. Flanks bounding sulcus moderately swol- 
len with steep posterolateral slopes but gentle anterior and lateral slopes. Noto- 
thyrial platform deep, cardinal process a simple septum; median ridge reaching 
slightly anterior to the middle, fairly stout. 
Measurements in mm.—Holotype, length 3.7, width 5.0, hinge width 3.9, thick- 
ness 3.7. 
Types.—Holotype: 110101a; figured paratypes: 110101b-e; unfigured para- 
types: 110101f-k. 
Horizon and locality —Effna-Rich Valley formations in Virginia: At Porter- 
field Quarry, 5 miles east of Saltville, Maccrady (T.V.A. 218-NW) Quadrangle. 
Discussion.—This species differs from P. mediocostata, with which it occurs, 
by its less transverse outline, less emarginate anterior margin, more slender and 
less depressed median costa, and the slight development of the apical plate of the 
pedicle valve. 
PTYCHOPLEURELLA SULCATA Cooper, new species 
Plate 50,I, figures 40, 41 
Species represented by two fairly well preserved specimens and a fragmentary 
one. Exterior usual for the genus; pedicle valve youthful, somewhat concave in 
lateral profile, broadly triangular in anterior profile; median costa prominent, 
larger than the others and with 2 intercalated ribs on each side forming a median 
fascicle. Flanks gently swollen and marked by 7 costae. 
Brachial valve moderately convex in lateral profile with the maximum con- 
vexity at the umbo; anterior profile broadly convex but with the median region 
deeply sulcate; sulcus originating at the umbo, deep, and deepening to the an- 
terior margin where it occupies slightly less than half the width; sulcus contain- 
ing 4 costae, 2 intercalated near the beak and the other 2 at about 1 mm. anterior 
to the beak. Flanks bounding sulcus narrowly but not strongly swollen; postero- 
lateral slopes steep. 
Measurements in mm.— 
Holotypes( brachial) valve) i>: ..; acuta. 2aitince vide beink 2 6.0 
Paratype (pedicle valve 110108b).......... sashpelareamimereto ni 3.3 5.5 
