364 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
(Pooleville member) of Oklahoma, but it is squarer and the ornamentation is 
finer. Furthermore, the sulcus of the Oklahoma species is wider and deeper than 
that of the Wisconsin form. 
GLYPTORTHIS BELLATULA Cooper, new species 
Plate 47, A, figures 1-8 
Shell of about medium size for the genus, length and width about equal; hinge 
slightly narrower than the greatest shell width which is located slightly anterior 
to the middle. Cardinal extremities obtuse ; lateral margins varying from nearly 
straight to sloping anterolaterally ; anterior margin broadly rounded. Anterior 
commissure rectimarginate. Surface marked by subangular, fairly broad cos- 
tellae separated by spaces about equal in width to the width of the costellae. Pos- 
terior half of shells marked chiefly by primary costellae, the secondary costellae 
appearing in the front half, one in each primary stria. Lamellae strong, distant, 
2 or 3 in a millimeter measured near the middle of the valve. 
Pedicle valve with lateral profile gently convex and with the greatest convexity 
located in the umbonal region; anterior profile broadly convex. Umbonal region 
subcarinate becoming flattened anteriorly to merge in the general convexity of 
the valve. Anterior slope long, moderately steep; lateral slopes convex, fairly 
steep. Interarea long, strongly apsacline. Teeth small, with deep fossettes. Den- 
tal plates short and receding ; muscular area not extending to the middle of the 
valve, not greatly thickened. Vascula media distinct, short. 
Brachial valve evenly convex in lateral profile and with the maximum con- 
vexity at about the middle; anterior profile broadly convex, slightly depressed 
medially. Umbonal region moderately convex; sulcus originating just anterior 
to the posterior margin, narrow and shallow, extending to the anterior margin 
or dissolving into the general convexity of the valve just posterior to the front 
margin. Flanks moderately convex with moderately steep slopes to the cardinal 
extremities but shorter and more gentle slopes to the anterolateral margins. In- 
terarea short, anacline ; median ridge carinate, extending slightly anterior to the 
middle. Brachiophores and cardinal process usual for the genus. 
Measurements in mm.— 
Hinge 
Length Width width Thickness 
Holotype (pedicle valve) ............ 123 13.7 11.9 4.3 
Paratype (brachial valve r110015e).... 10.7 12.6 10.0 2.8 
a (CET OOTS CY ete ciecait oelorent steers 8.9 TUF ? P 
Types.—Holotype: 110015a; figured paratypes: 110015d-h; unfigured para- 
types: 110015b,c. 
Horizon and locality—Chatham Hill formation in Virginia: Route 113 
(Marion-Chatham Hill road), 6 miles north of Marion, Chatham Hill (T.V.A. 
218-NE) Quadrangle. 
Discussion—See Glyptorthis assimilis. 
