PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 379 
Sevier formation in Tennessee: + mile northwest of Miser, Louisville (T.V.A. 
138-SE) Quadrangle. 
Discussion.—Of described species this one is most suggestive of G. multi- 
costellata, but it differs in having a less convex brachial valve and a more promi- 
nent sulcus on the brachial valve. It is also reminiscent of G. virginica, but that 
species is more coarsely costellated. 
GLYPTORTHIS UNIPLICATA Cooper, new species 
Plate 47, C, figures 13-17 
Shell of about medium size for the genus, slightly wider than long; hinge nar- 
rower than width at middle; sides nearly straight or gently rounded; anterior 
margin gently rounded; anterior commissure gently uniplicate; surface finely 
multicostellate ; costellae numbering about 55, subangular. 
Pedicle valve unevenly convex in lateral profile with the posterior third con- 
vex and the anterior two-thirds somewhat flattened; anterior profile broadly 
and gently convex ; umbonal and median regions swollen; anterior half occupied 
by a moderately deep and narrow sulcus that forms a short tongue; areas flank- 
ing sulcus gently swollen; lateral slopes short and moderately steep. Interarea 
gently curved, gently apsacline. 
Brachial valve gently convex in lateral profile but with the umbo fairly strongly 
curved ; anterior profile broadly and gently convex; umbonal and median region 
swollen; umbo sulcate, sulcus narrow and shallow, extending to a point slightly 
anterior to the middle where it merges in the general valve convexity to form 
an indistinct fold; sulcus occupied by about 8 costellae. Flanks bounding sulcus 
slightly swollen; posterolateral slopes gentle. 
Measurements in mm.— 
Hinge 
Length Width width Thickness 
Holotype (pedicle valve) ............. 13.4 14.3 12.3 5.4 
Paratype ( “ Piiib RAE GOA VA) at ex ose 10.9 12.8 11.6 3.8 
Types.—Holotype: 116947b; figured paratypes: 116947a,c; unfigured para- 
types : 116947¢,e. 
Horizon and locality.—Benholt formation (basal part of Echinosphaerites bed 
directly overlying the marble) in Virginia: 4 mile northeast of Speers Ferry, 
Clinchport (T.V.A. 188-NW) Quadrangle. 
Discussion.—This species is characterized by its rounded outlines and fine 
costellae. It is suggestive of G. bellarugosa but differs from that species in hav- 
ing a fairly prominent pedicle sulcus which is an unusual feature in this genus. 
The only other species with a marked pedicle sulcus is G. equiconvexa, but that 
is a thick-shelled and robust form having a subquadrate outline. 
GLYPTORTHIS VIRGINICA Cooper, new species 
Plate 48, D, figures 19-33 
Glyptorthis bellarugosa Wittarp (not Conrad), Bull. Mus. Comp. Zool., Harvard Coll., 
vol. 68, No. 6, p. 264, 1928. 
