PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 899 
MACROCOELIA PLEBEIA Cooper, new species 
Plate 121, G, figures 18, 19; plate 233, B, figures 4-6 
Shell small for the genus, wider than long and with the hinge slightly wider 
than the midwidth ; cardinal extremities auriculate. Sides slightly oblique; an- 
terior margin somewhat narrowly rounded. Surface marked by fine costellae 
set off into groups by stronger costellae, 2 of the stronger costellae occurring in 
I mm. and generally setting off groups of 3 or 4 of the finer costellae. 
Pedicle valve fairly strongly convex in lateral profile and with the maximum 
convexity at about the middle; anterior profile moderately convex and with the 
median region narrowly humped and with long lateral slopes. Umbo narrowly 
convex, the convexity continuing to the swollen median region where it is dissi- 
pated in the swelling; lateral slopes long, moderately steep; posterolateral ex- 
tremities flattened. 
Brachial valve gently concave and with the maximum concavity at about the 
middle ; sides and anterior margins somewhat flattened. 
Brachial interior with short and low median ridge, small and narrow cardinal 
process lobes and adductor ridges faintly developed. 
Measurements in mm.— 
Brachial Hinge Thick- 
Length length width Midwidth ness Height 
Halaty pe oFss ssvles Se 12.7 12.0 14.9 14.6-+- ? ? 
Paratype (117791)... 15.8 ? 18.0 18.3 ? 3.6 
Types.—Holotype: 117793a; figured paratypes: 117791, 117793b. 
Horizon and locality—Lenoir formation (Mimella-Valcourea zone) in Ten- 
nessee: In a small quarry between the Southern RR. tracks and U. S. High- 
way II, 14 miles southwest of Philadelphia, Philadelphia (T.V.A. 131-NW) 
Quadrangle; 0.9 mile west-northwest of Ellejoy Church, Wildwood (T.V.A. 
147-SE) Quadrangle; 45 feet above the base of the Lenoir, 0.1 mile southwest 
of triangulation mark 37SH, Wildwood (T.V.A. 147-SE) Quadrangle. 
Discussion.—This is a small species of moderate convexity. It is smaller and 
more quadrate than M. elegantula and is quite unlike any of the other species. 
It suggests Opikina, but the brachial valve is not geniculated. 
MACROCOELIA ROTUNDA Cooper, new species 
Plate 234, A, figures 1-5 
Rafinesquina cf. R. champlainensis Butts (not Raymond), Virginia Geol. Surv. Bull. 52, 
Dp. 85, pl. 86, figs. 5-7, 1942. 
Shell large for the genus, attaining a length of more than 2 inches; slightly 
wider than long; sides gently rounded; subparallel; hinge shorter or wider than 
the midwidth; cardinal extremities slightly auriculate. Anterior margin nar- 
rowly rounded. Costellae moderately strong, well differentiated into coarse and 
fine. 
Pedicle valve strongly convex in lateral profile and with the maximum con- 
vexity slightly anterior to the middle; anterior profile strongly domed, with 
