PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 863 
rowly rounded. Valves concavo-convex. Maximum width usually in the an- 
terior third. Surface marked by strong concentric lines of growth and minute, 
difficultly distinguishable radial lines which cancellate the delicate lines of growth. 
Pedicle valve moderately convex in lateral profile but with the umbonal region 
narrowly and strongly convex; anterior profile narrowly convex and with the 
sides nearly vertical or very steep and the median region narrowly rounded; 
umbo swollen ; interarea long, strongly anacline; pseudodeltidium short, strongly 
convex. Interior with dental plates reduced to ridges; vascula media deep and 
prominent, breaking into distributaries at the anterior third. 
Brachial valve deeply concave, the greatest depth located just anterior to the 
umbo ; sides strongly bent toward the brachial valve, anterior less strongly bent. 
Interior with flat brachiophores ; small cardinal process; median pair of ridges 
strong; lateral ridges somewhat less strong. 
Measurements in mm.— 
Brachial Hinge 
Length length Midwidth width Thickness Height 
Hypotype (117580a).... 13.2 8.8 0.4 vie 4.9 7.8 
ee (117580b).... 13.6 9.5 8.6 6.6 4.5 6.7 
oF (TL7550C)in. es 15.0 10.6 10.6 8.5 4.3 7.9 
a (257580d))...44105:0 Tier 10.0 27, 5.0 8.0 
53 (117580e).... 12.4 9.3 10.0 8.0 3.5 6.6 
a (117580f) .... 11.4 9.4 9.3 GE 3.0 6.0 
“ (117580g).... 8.7 7.0 oie) 6.1 25 4.8 
oi (117580h).... 82 6.3 ao 6.4 2.0 3.9 
*§ CVIPESOL) eo.  o 50 5.3 6.8 6.9 1.3 2.7 
* GIrr006))...2% 12.3 ? 8.5 Tegner ? 4.6 
- K7ISOE) 622508 137 10.7 11.0 8.6 37 6.4 
o (111016a).... 12.0 8.9 9.0 7.0 3.6 5.8 
as (111016b).... 13.6 9.4 7.9 6.8 4.1 6.8 
SY CTE 78) cic aie 10.3 7.8 8.4 8.4 4.0 6.3 
Types.—Figured hypotypes: 71501, 110999a, IIIO0I3a, IIIOI5, 111016a, 
I11017b, 111018a,b, 111020a-d, I1102I1a,c, 111029a, 117578, 1175709a, 117580}, 
123363, 123266a-g; measured specimens: 111006, I11016b, 117580a-i; figured 
specimen : 117577. 
Horizon and locality.—Little Oak formation in Alabama: 4 mile along High- 
way 31 northeast of Pelham, Bessemer Iron District (15’) Quadrangle; 3 mile 
northwest of Mosteller, St. Clair County; junction Bailey Gap and Cahaba 
Valley roads, SW4SW3 sec. 13, T. 19 S., R. 2 W., 13 miles northeast of New- 
hope Church, Vandiver (15’) Quadrangle. 
“Lenoir” limestone in Alabama: 20 feet below the Pratt Ferry formation, 0.15 
mile southeast of Pratt Ferry, Blocton (15’) Quadrangle. 
Pratt Ferry formation in Alabama: Same locality as above. 
Arline formation in Tennessee: At the Negro Cemetery, 4 mile northeast of 
Friendsville, Concord (T.V.A. 138-SW) Quadrangle; on the southeast edge of 
Friendsville and 1 mile northeast of Friendsville, Concord (T.V.A. 138-SW) 
Quadrangle; 5 miles southeast of Knoxville; on Kennedy Road, 0.4 mile north- 
west of Marbledale Church, Shooks Gap (T.V.A. 147-NE) Quadrangle; 1.500 
