368 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
cardinal process; low median ridge extending to the middle, and short, stout, 
flaring brachiophores. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
EIOIGE Pe cy de eee eens 8.7 8.6 11.0 9.5 5.0 
Paratype (116032c).. 10.5 10.1 12.8 10.9 4.6 
Types.—Holotype: 1169324; figured paratypes: 110054, 116932b; unfigured 
paratype: 116932c. 
Horizon and locality—Bromide formation (Mountain Lake member—bed 8) 
in Oklahoma: From a cut on Oklahoma Highway 18, center NW} sec. 11, T. 
1 S., R. 3 E., 1.8 miles south of Sulphur; Spring Creek, N4 sec. 17, T. 2 S., 
R. 1 W.; Murray County. 
Discussion—This species is characterized by its subcarinate pedicle valve and 
the fairly deep and narrow sulcus on the brachial valve. It differs from G. costel- 
lata of higher Bromide beds in somewhat smaller size, less robust form, narrower 
profiles, and somewhat more delicate ornamentation. It is a much larger and 
more elongate shell than G. uncinata from the lower Bromide (Mountain Lake 
member ). 
GLYPTORTHIS EQUICONVEXA Cooper, new species 
Plate 47, D, figures 18-30; plate 108, C, figures 15-18 
Shell fairly large for the genus, subquadrate in outline but with the width 
slightly greater than the length; valves of nearly equal depth; anterior com- 
missure broadly uniplicate ; hinge narrower than the width at the middle; sides 
nearly straight; anterolateral extremities narrowly rounded; anterior margin 
gently rounded to somewhat truncated. Surface costellate ; costellae unequal in 
size, appearing in 4 generations; about 5 costellae in 5 mm. at the front margin; 
imbrications fairly closely crowded. 
Pedicle valve fairly strongly and evenly convex in lateral profile with the 
greatest convexity at about the middle; anterior profile swollen in the median 
region and with gently dipping lateral slopes. Beak incurved ; umbo swollen and 
with steep umbonal slopes; sulcus originating about 4 mm. anterior to the beak, 
deepening and widening anteriorly but never attaining great depth; width of 
sulcus about one-third shell width. Flanks bounding sulcus gently swollen; pos- 
terolateral slopes short, moderately steep. Interarea moderately long, almost 
orthocline, gently curved; beak incurved; delthyrium narrow. 
Brachial valve unevenly convex in lateral profile with the umbonal region 
strongly curved but the remainder of the valve gently convex; anterior profile 
swollen and fairly evenly convex; umbo strongly curved and swollen; umbo 
sulcate, sulcus narrow, short, becoming obsolete about 6 mm. anterior to the 
beak; fold low, indistinctly defined from about 6 mm. anterior to the beak to 
the front margin; flanks bounding fold inflated; umbonal slopes to the small de- 
pressed posterolateral areas short and steep. Beak strongly incurved; interarea 
short and curved. 
