PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 789 
Ward Cove formation in Virginia: 0.4 mile northeast of Jeff Gillespie’s, 
Thompson Valley, west-southwest of Tazewell, Pounding Mill (15’) Quad- 
rangle. 
Lower Chatham Hill formation in Virginia: On the Grayson Farm, 4 miles 
southwest of Bland; 6 miles southwest of Bland; Bland County. 
Whitesburg formation in Tennessee: 14 miles northeast of Bulls Gap, Bulls 
Gap (T.V.A. 171-SE) Quadrangle. 
Discussion.—Sowerbyella negritus is best characterized by its ornamentation, 
the depth of its valves, and the pointed cardinal extremities. The ornamentation 
consists of strong costellae separated by 2 to 8 finer costellae, the higher num- 
bers of finer costellae predominating. The shell is also well wrinkled along the 
posterior margin. In addition to these features a crude, obscure plication ap- 
pears in some of the shells, particularly the median part of the pedicle valve which 
is often strongly folded. 
Few species have been described that can be compared to this one. It is close 
to S. perplexa, but that species is generally more convex, does not have a promi- 
nent median fold, and the strong costellae are separated by a smaller number 
of the fine radii. 
SOWERBYELLA PARVA Cooper, new species 
Plate 202, B, figures 9-15 
Shell small for the genus, wider than long, semielliptical in outline; sides 
nearly straight to gently convex ; anterior margin rounded; widest near the mid- 
dle in the adult; cardinal extremities nearly a right angle, rarely auriculate; 
finely costellate, costellae fairly even in size but somewhat differentiated into 
larger and smaller ones at the front margin: 6 to 7 costellae in I mm. at the front 
margin. 
Pedicle valve moderately convex in lateral profile; anterior profile rising to a 
low crest medially and with long, flat, moderately dipping slopes. Umbo nar- 
rowly swollen; median fold absent or obscure; flanks gently inflated; interarea 
strongly apsacline. 
Brachial valve with a poorly defined concave sulcus extending from the con- 
cave umbo to the front margin ; center of valve most deeply concave part; flanks 
gently concave, lateral and posterolateral regions flattened. 
Pedicle interior with short but strong median septum dividing subflabellate 
diductor fields; pallial trunks moderately developed. Brachial valve moderately 
thickened ; septa moderately elevated at the middle of the valve; anterior slope 
not strongly thickened. 
Measurements in mm.— 
Brachial Hinge 
Length length Midwidth width Thickness Height 
Plolotype? te. fees sete ces 6.5 6.1 9.0 8.7 1.4 1.9 
Paratype (117507b) ... 7.0 6.6 0.4 8.9 1.7 2.2 
Types——Holotype: 117507a; figured paratypes: 117507b-d. 
Horizon and locality—Ward Cove formation in Virginia: In small cemetery 
