PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 555 
margin. Tongue short and broadly rounded. Plicae bounding sulcus moderately 
strong ; flanks nearly flat and with gentle slopes. Interarea long, gently apsacline. 
Brachial valve gently and evenly convex in lateral profile but with a swollen 
umbonal region ; anterior profile broadly and gently convex. Fold originating just 
anterior to the umbo, low and narrow, expanding anteriorly; fold only mod- 
erately elevated above the flanks, most strongly elevated at the front. Flanks 
gently inflated and with moderate slopes to the margins. 
Measurements in mm.—Holotype, length 21.4, brachial length 19.0, width 
24.0, hinge width 14.3, thickness 10.0. 
Type.—Holotype: 117122. 
Horizon and locality.—Carters formation (O.roplecia bed) in Alabama: In the 
quarry 0.3 mile north of Gate City, Leeds (15’) Quadrangle. 
Discussion.—This is a large species with strong costellae but it differs mark- 
edly from all the other large forms described herein in the strongly erect beak 
of the pedicle valve, the long interarea, and the shallowness of both valves. The 
species has an exceptionally compressed profile for such a large form. 
OXOPLECIA PLICATA Cooper, new species 
Plate 104, E, figures 25-31 
Shell small for the genus, transversely elliptical in outline with narrowly 
rounded lateral margins and broadly truncated anterior margin. Hinge wide, 
equal to more than half the shell width. Surface costellate, the sulcus occupied 
by 4 costellae and the fold by 6. Flanks marked by about 18 costellae. 
Pedicle valve gently convex in lateral profile with the greatest curvature in 
the umbonal region. Beak prominent, elongated ; posterior median half of valve 
gently convex ; sulcus originating at about the middle, deepening rapidly and oc- 
cupying about half the width at the front margin. Slopes into sulcus deep and 
abrupt ; flanks bounding sulcus gently convex with gentle slopes to the margins ; 
slopes to cardinal extremities steeper than those to margins but gentle neverthe- 
less. Ridge on pseudodeltidium prominent ; interarea curved, apsacline. 
Brachial valve strongly convex in lateral profile, about three times as deep as 
the pedicle valve. Fold originating about one-third the length from the beak; 
umbonal region slightly swollen ; beak low and inconspicuous. Fold strongly ele- 
vated in the anterior portion with steep and abrupt slopes to the flanks, which 
are strongly convex and have steep slopes to the margins. 
Measurements in mm.—Holotype, length 9.1, brachial length 8.7, width 11.8, 
hinge width 7.0, thickness 7.1. 
Type.—Holotype: 117123. 
Horizon and locality—Red Knobs formation in Tennessee: # mile east of 
Friendsville, Louisville (T.V.A. 138-SE) Quadrangle. 
Discussion.—This species is characterized by its small size, narrowly and trans- 
versely elliptical outline, and fine costellae. It has some of the features of small 
specimens of O. holstonensis but is wider and more distinctly marked. 
