PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 795 
197-NE) Quadrangle; on the west slope of the hill 4 mile east of Cedar Point 
School, Hilton (T.V.A. 197-NW) Quadrangle ; south side Mount Hagan School, 
Hilton (T.V.A. 197-NW) Quadrangle; + mile east of Speers Ferry, Clinchport 
(T.V.A. 188-NW) Quadrangle. 
Same formation in Tennessee: On the north side of the road 1.1 miles north- 
east of Lee Valley, Lee Valley (T.V.A. 171-NW) Quadrangle. 
Discussion.—This species most closely resembles P. superba of the species de- 
scribed in this monograph but differs in its larger size, thick valves, and more 
rounded front margin. The anterior margin of P. superba is narrowly rounded 
to subnasute with lateral margins sloping inward. P. superba is somewhat more 
concave in the geniculated region than P. resupinata but is much less convex on 
the brachial side. 
PALAEOSTROPHOMENA ? RUGOSA Cooper, new species 
Plate 176, B, figures 6-12 
Shell large for the genus, wider than long, strongly resupinate; hinge form- 
ing the greatest width and with acute cardinal extremities. Sides nearly straight 
to oblique ; anterior margin strongly rounded. Surface costellate, costellae in two 
sets, a larger group in a field of fine costellae; 6 or 7 of the larger costellae in 
5 mm. at the front margin. Posterior margin marked by strong, oblique wrinkles ; 
disk region of both valves marked by chevron-shaped wrinkles confined between 
2 of the larger costellae. 
Pedicle valve with posterior half convex in lateral profile but anterior half 
strongly concave ; umbo and surrounding region moderately swollen ; most deeply 
concave at about valve middle where shell geniculates in the direction of the 
pedicle valve; sides and anterior half bent strongly in the direction of the pedicle 
valve ; interarea moderately long, apsacline. Interior with long, slightly divergent 
diductor scars. 
Brachial valve fairly deeply concave in the umbonal and median regions to 
about the middle of the valve where it is bent strongly toward the pedicle valve. 
Angle of geniculation about 135°. Sides and anterior half gently convex in pro- 
file and forming steep lateral and anterior slopes. Interior with bulbous cardinal 
process, long and low median ridge most elevated at anterior end slightly anterior 
to the valve middle ; brachiophores thin, small, orthoid. Myophore strongly tri- 
lobed. Pallial impressions forming deep and narrow channels. 
Measurements in mm.— 
Brachial Hinge 
Length length Midwidth width Thickness 
Bile 0S. EN SAR 13.8 13.6 16.9 18.6 sie 
Baratype.. (127378a) vi oes ainwaye 14.7 ? 19.4 ? 22.3 o 
Types.—Holotype: 117379c ; figured paratypes: 1173709a,e-g ; unfigured para- 
types: 117378a-c, 117370b,d. 
Horizon and locality—Botetourt formation in Virginia: On the south side of 
U. S. Highway 60, about 1 mile northwest of Lexington, Lexington (15’) 
Quadrangle. 
