PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 847 
Brachial valve nearly flat in lateral profile, interior with bilobed, cardinal 
process, 4 adductor septa and a thickened inner rim. 
Measurements in mm.— 
Brachial Hinge 
Length length Midwidth width Thickness 
Holotype (pedicle valve)........... 14+ if 15.4+ 14.8 4.6 
Paratype (pedicle valve 117636b).. 19.3 ? 22.4 20.0 5.4 
“ (brachial valve 117637a)..  ? 12.3 17.0 15.5 1.5 
4 G..e5 Ge 2 nr703z6e it StF 18.5 25.7 21.5 2.0 
Types——Holotype: 117636a; figured paratypes: 117632a, 117633, 117635¢, 
117636b-f, 117637a,b; unfigured paratypes: 117632b,c, 117635a,b, 117636g,h, 
117637¢,d. 
Horizon and locality—Wardell formation in Tennessee: In Raccoon Valley, 
3 mile northeast of Fleanor Mill, Powell Station (T.V.A. 137-SE) Quadrangle. 
Dryden formation (and Wardell part) in Tennessee: Along the road to 
Tazewell 14 miles northeast of Lone Mountain, Tazewell (T.V.A. 154-NE) 
Quadrangle. 
Poteet formation (Yellow Branch member) in Virginia: Along the road beside 
Yellow Branch, 5 miles southeast of Rose Hill, Rose Hill (T.V.A. 161-NE) 
Quadrangle. 
Discussion.—This species is characterized by its large size and generally plano- 
convex profile. It is most like M. partita from the Bromide formation of Okla- 
homa but differs in being less convex and in having a more extravagant de- 
velopment of the median ridge inside the brachial valve. The septa associated 
with the adductor scars in M. muralis are more prominently developed than they 
are in M. partita. Inside the pedicle valve of M. muralis the dental plates are 
somewhat more fully developed. The greatest width of M. muralis is nearer the 
hinge whereas in M. partita it is nearer the middle. 
MURINELLA PARTITA Cooper, new species 
Plate 223, F, figures 11-17; plate 227, D, figures 17-25 
Shell large, variable, wider than long; planoconvex to biconvex, the pedicle 
valve being the deeper; greatest width at or near the middle; sides gently 
rounded; anterior margin broadly rounded; surface marked by costellae of un- 
equal size, the larger ones separated by 2 to 4 of the finer ones. 
Pedicle valve moderately convex in lateral profile and with the maximum 
convexity at about the middle; anterior profile moderately domed in the median 
region and with long, moderately steep lateral slopes; umbonal region swollen ; 
median region swollen; anterior and lateral slopes subequal, moderately steep. 
Interior with subcircular muscle field confined to the posterior third; diductor 
scars somewhat elongated anteriorly ; median ridge long and slender. 
Brachial valve varying from gently convex to nearly flat in lateral profile; 
umbo concave, the concavity continued anteriorly at least to the middle as a 
shallow sulcus; flanks flat or gently convex ; Interior with stout cardinal process ; 
