PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 457 
DOLEROIDES CRASSUS Cooper, new species 
Plate 95, A, figures 1-5 
Shell of about medium size for the genus, subquadrate in outline; hinge nar- 
row ; greatest width anterior to the middle; sides oblique outward ; anterolateral 
extremities narrowly rounded; anterior margin broadly rounded ; anterior com- 
missure rectimarginate. Costellae appearing in 4 generations; about 9 to I0 
costellae in 5 mm. at the front margin. 
Pedicle valve about equal in depth to that of the brachial valve; moderately 
convex in lateral profile but with the anterior third somewhat flattened; beak 
somewhat elongated; umbo not differentiated from the inflated median region; 
sides somewhat inflated ; posterolateral slopes short and steep. 
Brachial valve fairly strongly convex and with the maximum curvature at the 
middle ; anterior profile broadly convex with a flattened median region and short, 
steep lateral slopes ; median ridge shallow, narrow, and confined to the posterior 
half; flanks moderately swollen; posterolateral slopes short and steep. 
Measurements in mm.—Holotype, length 15.5, brachial length 14.7, width 18.3, 
hinge width 13.2, thickness 9.0. 
Types—Holotype: 110742b; unfigured paratype: 110742a. 
Horizon and locality—Ridley formation in Georgia: from a road cut on 
U. S. Highway 27 just northwest of Chickamauga Creek, Kensington (T.V.A. 
106-SE) Quadrangle. 
Discussion.—This species is characterized by its narrow hinge that differenti- 
ates it from D. extensus with which it occurs. Its form is suggestive of that of 
D. gibbosus of the Upper Mississippi Valley and Canada, but it differs from 
that species in its rectimarginate anterior commissure, less deep valves, and some- 
what stronger costellae. 
DOLEROIDES EXTENSUS Cooper, new species 
Plate 95, B, figures 6-20 
Shell fairly large for the genus, somewhat rectangular in outline; wider than 
long, with the hinge only slightly less than the midwidth; sides gently rounded ; 
anterior margin broadly rounded ; anterior commissure rectimarginate ; costellae 
thick, narrowly rounded, appearing in several generations and numbering about 
II in 5 mm. at the front of the holotype. 
Pedicle valve slightly deeper than the brachial valve, gently convex in lateral 
profile; broadly convex in anterior profile with the median region somewhat 
narrowly rounded ; beak low ; umbo somewhat inflated ; median region moderately 
swollen ; lateral areas gently convex and with long, gentle slopes to the margins. 
Interarea apsacline; interior with short and flaring dental plates; umbonal cavi- 
ties shallow ; muscle field extending nearly to the middle, typical for the genus. 
Brachial valve gently convex in lateral profile; anterior profile broadly convex 
with gently depressed or flattened median region and short, steep lateral slopes ; 
umbo and median region gently swollen; sulcus shallow and narrow, originating 
on the umbo but extending only to the middle where it merges with the some- 
