PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 372 
Measurements in mm.— Hinve 
Length Width width Thickness 
Holotype (pedicle valve) ............. 10.0 12.5+ 12.0 4.0 
Paratype ( “ i, PIRLOOSOR) we ass 3 10.3 12.1 ? ? 
- (brachial valve 116036e)..... 10.2 13.8 12.4 3.0 
i Cer ona NPVEGSOU 2. > « 8.4 12.3 11.9 1.6 
Types.—Holotype ; 116936a; figured paratypes: 116936d,e; unfigured para- 
types: 116936b,c,f. 
Horizon and locality Wardell formation in Tennessee: In Raccoon Valley, 
$ mile northeast of Fleanor Mill, Powell Station (T.V.A. 137-SE) Quadrangle. 
Pierce formation in the Central Basin of Tennessee: At Pierce Mill, 74 miles 
north of Murfreesboro, Rutherford County. 
? Lebanon formation in the Central Basin of Tennessee: On Tennessee High- 
way 16, 5.1 miles north-northwest of Shelbyville, Bedford County. 
Discussion.—This is a somewhat variable species characterized by a fairly deep 
pedicle valve but a very shallow brachial valve. It is suggestive of G. assimilis, 
but that is a more robust form having more nearly equally deep valves. 
Glyptorthis virginica is similar but differs in more robust form, a more promi- 
nent brachial sulcus, and deeper brachial valve. 
GLYPTORTHIS MULTICOSTELLATA Cooper, new species 
Plate 46, F, figures 35-40 
Shell large for the genus, wider than long; valves subequally convex; hinge 
narrower than the greatest shell width at the middle; sides gently rounded; 
anterior margin broadly rounded; anterior commissure rectimarginate ; surface 
multicostellate ; costellae uneven in size, the primary ones the larger and sur- 
rounded by finer costellae of several generations ; about 10 costellae in 1 mm. at 
the front margin. Imbrications about 3 to the millimeter. 
Pedicle valve gently convex in lateral profile with the maximum convexity in 
the median half; anterior profile broadly convex ; umbonal region slightly swollen ; 
median region gently convex; lateral and posterolateral slopes gentle. Interarea 
flat, almost catacline ; delthyrial cavity wide and deep; anterior ends of diductor 
scars extended anterior to delthyrial cavity ; dental plates well developed ; adduc- 
tor track short, somewhat elevated. 
Brachial valve moderately convex in lateral profile with the greatest convexity 
in the median region; anterior profile broadly but moderately convex ; umbonal 
and median regions swollen; umbo sulcate; sulcus narrow and moderately deep 
but shallowing and disappearing near the front margin; flanks bounding sulcus 
moderately swollen; posterolateral areas somewhat flattened; posterolateral 
slopes moderately steep, short. Notothyrial platform thickened ; brachiophores 
stout and short; cardinal process prominent, stout. 
Measurements in mm.— 
Hinge 
Length Width width Thickness 
Holotype (pedicle valve).............. 11.9 16.9 14.5 3.9 
Paratype (brachial valve 116938c)...... 127 16.4 14.1 3.0 
