PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 931 
the formation in Marshall Knobs, 5 miles south of Murfreesboro, Murfreesboro 
(15’) Quadrangle. 
Discussion.—This species is characterized by moderate convexity and con- 
cavity, thin body cavity, long interarea, well-rounded muscle area and fine, well- 
differentiated costellae. It differs from S. medialis in the finer ornamentation 
and more convex valves. It differs from S. grandimusculosa in the form and 
less thickening of the muscle area, the more rectangular cardinal extremities, 
differentiated ornamentation, and greater convexity. Strophomena musculosa 
from the Decorah shale is more convex and has a wider muscle field in the pedicle 
valve. The form and outline of S. costellata are similar, but the ornamentation 
of that species consists of costellae less differentiated in size than in the Ridley 
species. 
STROPHOMENA BASILICOIDEA Cooper, new species 
Plate 256, A, figures 1-5 
Shell large, subrectangular in outline; hinge forming the greatest width; sides 
nearly straight but indented gently anterior to the cardinal extremities. Anterior 
margin broadly rounded. Costellae rounded, subequal, somewhat distant and 
alternating in size, about 13 to I5 in 5 mm. at the front margin. 
Pedicle valve moderately concave in lateral profile; maximum concavity in the 
median third; umbo narrowly convex and with a short fold; umbo-lateral areas 
gently concave; median third deeply concave but anterior third more gently 
concave; interarea fairly long; pseudodeltidium narrowly convex, subcarinate. 
Brachial valve evenly and strongly convex in lateral profile; broadly and mod- 
erately convex in anterior profile; maximum convexity at about the middle; 
posterior third somewhat flattened. Umbo marked by a short, narrow, shallow 
sulcus. Median region swollen; anterior slope convex, moderately long and 
steep ; lateral slopes moderately long and steep. Interior with delicate cardinalia. 
Measurements in mm.—Holotype, length, 25.6, brachial length 23.9, midwidth 
31.0, hinge width ?, thickness 3.8. 
Type.—Holotype: 117706. 
Horizon and locality—Peery formation in Virginia: On U. S. Highway 109, 
400 feet west of the junction with Virginia Highway 650, Wittens Mills, Burkes 
Garden (15’) Quadrangle. 
Discussion.—This species is somewhat like S. basilica but differs in more 
closely crowded, stronger costellae and in having a more uniformly inflated 
brachial valve and a somewhat more concave pedicle valve. 
STROPHOMENA BELLILINEATA Cooper, new species 
Plate 262, A, figures 1-7 
Shell large, slightly wider than long ; subquadrate in outline ; cardinal extremi- 
ties slightly alate; sides nearly straight except for a gentle indentation just an- 
terior to the cardinal extremities; anterior margin broadly rounded. Surface 
beautifully sculptured and consisting of strong costellae setting off groups of 
10 to 12 finer ones; 4 of the stronger costellae appear in a space of 10 mm. at 
the anterior margin of a specimen 26 mm. long. 
