PART, tT CHAZYAN AND RELATED BRACHIOPODS—COOPER 373 
Pedicle valve much deeper than the brachial valve and having a fairly long, 
nearly procline interarea. Most convex at the umbo with long, gently concave 
umbonal slopes. 
Brachial valve very gently convex in both profiles and marked medially by a 
shallow, narrow sulcus which originates at the umbo and extends to the front 
margin. Sulcus occupied by a single costa. 
Measurements in mm.—Holotype, length 5.4, brachial length 5.1, midwidth 
8.4, hinge width 8.2, thickness 3.6. 
Types.—Holotype: 110069a ; unfigured paratype: 110069b. 
Horizon and locality.— Benbolt formation in Virginia: 1 mile west of Rye 
Cove, Clinchport (T.V.A. 188-NW) Quadrangle. 
Discussion—The strong costae, few imbrications, and great width of this 
little species distinguish it from G. glypta and G. concinnula which are both of 
small size. 
GLYPTORTHIS SENECTA Cooper, new species 
Plate 45, B, figures 7-14 
Small for the genus, strongly biconvex, slightly wider than long; cardinal ex- 
tremities nearly a right angle or slightly obtuse ; hinge slightly narrower than, or 
nearly equal to, the width of the valves at the middle where the maximum width 
is located. Lateral margins nearly straight; anterior margin broadly rounded ; 
anterior commissure uniplicate. Surface finely costellate, 4 to 7 costellae occupy- 
ing a space of 2 mm. at the anterior margin. Concentric lamellae fairly closely 
crowded but variable. 
Pedicle valve moderately convex in lateral profile, but strongly convex in an- 
terior profile. Beak prominent ; umbonal region convex ; median region nearly to 
front fairly strongly swollen and with steep sides descending to the front and lat- 
eral margins. Interarea long, apsacline. Muscle field with elongate and narrow 
diductor scars; adjustor impressions small, located at base of dental plates, not 
distinct. Adductor track wide, often strongly elevated. Dental plates receding. 
Brachial valve slightly less convex in lateral profile than the pedicle valve; 
broadly convex in anterior profile. Umbonal region convex, sulcus originating on 
umbo, shallow, widening to about the middle where it is lost in the anterior third. 
Flanks convex with moderately steep slopes. Inside the dorsal valve the median 
ridge extends to a point slightly anterior to the middle. Cardinalia strong and 
typical for the genus. 
Measurements in mm.— 
Hinge 
Length Width width Depth 
Holotype (pedicle valve)........... 9.2 10.1 9.4 4.6 
Paratype ( “ “ yroozary 2° o7 10.1 8.8 3.6 
ss (brachial valve 110070g).. 7.5 9.5 9.4 2.8 
‘ eS * UTLOOZOe))..., 7.0 8.5 8.0 2.4 
Types——Holotype: 110070h; figured paratypes: 110070c,d,f,g,1; unfigured 
paratypes : 110070a,b,e. 
Horizon and locality—Poteet formation (Yellow Branch member=9-foot 
