PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 749 
pallial trunks slender, divergent, not deeply impressed and extending to about 
the middle. Brachiophores short, slender; median ridge slender, well elevated ; 
visceral disk wide, occupying the posterior two-thirds to three-fifths of the valve. 
Muscle marks not deeply impressed. 
Measurements in mm.— 
Brachial Hinge 
Length length Midwidth width Thickness 
PRIEST eer ce icin trie dx ws aaiecete es cna e 7.4 6.4 8.9 8.9 2.5 
Paratype Cri7agsa) eer cc. ec ereieeet 6.0 ? 72 8.9 ? 
Wy GUTGA SRD acs eo lester a ous 6.3 P 8.3 9.6 ie 
ae (brachial valve 117435d).... ? 5.3 8.2 85 ? 
Types.—Holotype: 117434c; figured paratypes: 117434b, 117435b,c,f; un- 
figured paratypes: 117434a, 117435a,d,e,g-1. 
Horizon and locality— Whitesburg formation in Tennessee: 15 miles west of 
Bulls Gap, Bulls Gap (T.V.A. 171-SE) Quadrangle. 
Chatham Hill formation in Virginia: Grayson Farm, 4 miles southwest of 
Bland, Bland County. 
Discussion.—This is a small and beautifully marked species characterized by 
the fairly close crowding of the major costellae on the anterior slope and the 
prominence of the median costella. This species is unlike any other described 
in its ornamentation. It is suggestive of L. tennesseensis in ornamentation, but 
that species attains twice the size of L. bella. 
LEPTELLINA DELICATULA (Butts) 
Plate 188, C, figures 13, 14; plate 191, D, figures 32-39 
Plectambomites delicatula Butts, Alabama Geol. Surv., Special Rep. 14, p. 116, pl. 26, figs. 20, 
21, 1926. 
Plectambonites cf. P. pisum Butts, idem, p. 116, pl. 26, figs. 18, 19, 36, 37, 1926. 
Shell of about medium size for the genus, subquadrate in adult outline, a little 
wider than long; cardinal extremities acute to obtuse depending on age and 
preservation. Lateral margins rounded, oblique to nearly straight. Front mar- 
gin narrowly rounded. Surface marked by costellae of 3 sizes. In young speci- 
mens 5 large costellae stand out over a field of very fine costellae. In adults 
many costellae of intermediate size are intercalated on the anterior slope and 
number about 40. These are separated by the finest costellae about 7 in a milli- 
meter measured at the front of the brachial valve of an adult. 
Pedicle valve strongly convex in lateral profile with the greatest convexity 
located at about the middle; anterior profile a strongly convex bow equal in 
height to about half the width of the shell. Umbo and beak inconspicuous ; middle 
and anterior portions strongly swollen; lateral slopes descending steeply to the 
lateral and cardinal extremities. Interarea long, orthocline, slightly curved. 
Pseudodeltidium short, strongly arched. 
Brachial valve deeply concave with the greatest concavity at about the center ; 
lateral and anterior portions strongly elevated to form a deep cup. Valve shallow 
at cardinal extremities which are somewhat flattened. Lateral margins sloping 
