PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 755 
the sulcus gently convex to flattened depending on the age. Interarea short, 
hypercline. 
Interior: Muscle area of pedicle valve small, deeply impressed, equal to about 
one-fourth the width and one-fifth the length. Dental plates short, umbonal cavi- 
ties well filled by callus in the adult. Vascula media of the pallial system short, 
not deeply impressed. Ridge anterior to muscle field fairly high, thin and well 
anterior of the muscle field. Brachial valve with only moderately large visceral 
area which extends anteriorly to about the middle of the valve, and is produced 
forward as an overhanging ledge for a short distance. Median ridge broad and 
low. Muscle marks not well impressed. 
Measurements in mm.— 
Brachial Hinge 
Length length Midwidth width Thickness 
PANG ENES EO ae 8 8 sities ares s-chpasiare, om 8.0 ? 9.9 13.8 ? 
Paratype (pedicle valve 117446f) ... 10.3 ? 13.4 14.1 ? 
af (brachial valve 117446b).. ? 78 12.3 12.8 ? 
Types.—Holotype: 117446a; figured paratypes: 117446b,c,f-h; unfigured 
paratypes: 117446d,e,i-k. 
Horizon and locality—Base of Athens formation in Tennessee: 24 miles 
south-southeast of Riceville, Calhoun (T.V.A. 125-SW) Quadrangle; 2 miles 
south of Philadelphia, Philadelphia (T.V.A. 131-NW) Quadrangle; 600 feet 
S. 40° E. of the railroad crossing 1 mile northeast of the courthouse in Athens, 
Athens (T.V.A. 125-SE) Quadrangle; 0.2 mile southeast of Britton Church, 
24 miles northeast of Calhoun, Calhoun (T.V.A. 125-SW) Quadrangle. 
Discussion.—This species is known only from the base of the Athens shale 
in the belt running through Athens, Tenn. The species has moderate convexity, 
a somewhat keeled pedicle valve, small muscle field in the pedicle valve, and the 
visceral disk not strongly overhanging the trail. The species is nearest L. tennes- 
seensis but never attains the large size of that species nor its great convexity. 
LEPTELLINA SUBLAMELLOSA Cooper, new species 
Plate 188, B, figure 12; plate 188, D, figures 15-24; plate 190, B, figures 5-8; 
plate 190, C, figures 9-25 
Small, wider than long and with the hinge forming the widest part; cardinal 
extremities acute ; sides oblique, gently rounded ; anterior margin broadly to nar- 
rowly rounded; surface finely costellate, costellae of unequal size; part or most 
of surface covered by closely spaced wavy lamellae. 
Pedicle valve with strongly convex lateral profile, the maximum convexity 
located at or near the middle; anterior and lateral slopes nearly equal in length 
and nearly equal in steepness; anterior profile ranging from moderately to 
strongly convex in the median region and with long, steep lateral slopes. Beak 
small; umbo and median regions swollen. Interarea moderately long, orthocline. 
Interior with short but deeply impressed muscle scars; vascula media incon- 
spicuous. 
Brachial valve fairly strongly concave particularly in the median region and 
