PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 325 
Discussion—tThis species differs from C. magna in its quadrate outline and 
stronger costellation; it differs from C. bella in its more rounded margins and 
its stronger concavity of the brachial valve. 
CYRTONOTELLA VIRGINIENSIS Butts 
Plate 40, C, figures 12-21; plate 40, D, figures 22-26 
Cyrtonotella virginiensis Butts, Virginia Geol. Surv. Bull. 52, pt. 2, p. 67, pl. 80, figs. 20, 21, 
1942. 
Shell large, strongly concavo-convex; wider than long with a hinge wider 
than the shell at the middle. Cardinal extremities nearly a right angle to slightly 
acute. Lateral margins sloping slightly toward the middle; anterior margin 
broadly rounded. Anterior commissure not folded. Surface multicostellate, cos- 
tellae appearing in 4 generations, all narrowly rounded, and separated by striae 
about equal in width to the width of the costellae, about 80 costellae at the front 
margin of an adult and about 7 to 9 in 5 mm. at the median portion of the front 
margin. Costellae with a tendency to fasciculation along the margin. 
Pedicle valve moderately convex in lateral profile with the greatest convexity 
located in the umbonal region which is strongly curved. Anterior profile un- 
evenly convex with the maximum convexity in the median region and the sides 
descending moderately. Median region swollen from umbo nearly to front mar- 
gin with gentle slopes to anterior and lateral margins. Interarea short, strongly 
curved. Muscle area subquadrate with length and width about equal. Diductor 
impressions large; adductor field elongate, very narrow. 
Brachial valve moderately concave with the maximum concavity between the 
median region and the anterior margin. Umbonal region flattened; the area an- 
terior to the umbo slightly depressed to form a barely perceptible sulcus which 
is lost in the concave anterior half. 
Flanks flat to slightly concave ; cardinal extremities flattened. Interarea short, 
hypercline. Interior with short median ridge extending for about one-third the 
valve length. Brachiophores very short, widely divergent. Cardinal process short, 
small. Notothyrial edges with traces of low chilidial plates. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
Hypotype (complete specimen 109865b). 20.5 18.1 26.3 26.8 3.0? 
i (pedicle valve 109863)....... 21.6 ? 28.3 20.7 3 
72 (brachial valve 116894a)..... 2 16.9 22.4 25.2 ? 
Types.—Lectotype: 99263a; paratype: 99263b; figured hypotypes: 109863, 
109865a,c, 109868a,b,e, 109870c; unfigured hypotypes: 109865b, 109868c,d, 
109870a,b, 116894a,b; figured specimen: 109872. 
Horizon and locality—Botetourt formation in Virginia: Northeast of Ca- 
tawba ; junction of Virginia Highways 311 and 114, 4 mile southwest of Catawba, 
Salem (15’) Quadrangle. 
Arline formation in Tennessee: North side of wagon road in glade, 4 mile 
southeast of Friendsville, Concord (T.V.A. 138-SW) Quadrangle. 
