PART I CHAZYAN AND RELATED BRACHIOPODS—-COOPER 367 
Measurements in mm.— 
Dorsal Hinge 
Length length Width width Thickness 
Holotypeils hess ae 12.1 11.4 13.8 Til. 6.2 
Paratype (110045a).. 10.5 10.0 11.3 11.0 5.5 
* (110040a).. 9.3 8.8 10.8 8.8 5.0 
- (t10040b).. 8.1 8.0 9.6 8.5 4.5 
(110059a).. 12.2 11.3 13.8 10.4 6.8 
H (110059c).. 12.8 11.6 14.6 1277 7.0 
Types.—Holotype: 110052a; figured paratypes: 110038a, 110040a,b, 110052b, 
110059a,b; unfigured paratypes: 110038b-d, 110040c-d, I110045a, I10059¢. 
Horizon and locality.—Bromide formation (Pooleville member-O-oplecia 
gouldi zone) in Oklahoma: On a branch of Hickory Creek, NW} sec. 26, T. 
5 Ss. R. 1 E,, east side of Criner Hills; Rock Crossing of Hickory Creek, 
NELSW35 sec. 35, T. 5 S., R. 1 E.; Criner Hills, Carter County. 
Discussion.—Specimens of this species from section 26 along a small branch 
of Hickory Creek are exceptionally well preserved and show the lamellae to per- 
fection. Where the lamellae cross the costellae, they are pinched into narrow 
spinelike folds. Perfect young specimens are obtainable here and are generally 
transverse. 
Glyptorthis costellata is suggestive of G. sulcata in its quadrate outline, but 
the valves are not so convex, the sulcus of the brachial valve is less wide and 
shallower, the palintrope is not so elongated, and the lamellae are coarser. 
GLYPTORTHIS CRENULATA Cooper, new species 
Plate 44, C, figures 11-19 
Shell of about medium size for the genus, wider than long with the maximum 
width in the midregion; hinge narrower than the greatest shell width; cardinal 
extremities obtuse; sides moderately rounded; anterior margin nearly straight ; 
anterior commissure narrowly sulcate; surface multicostellate, costellae about 2 
to the millimeter at the front margin ; imbrications distant, about 2 or 3 in I mm. 
Pedicle valve gently convex in lateral profile and with the maximum convexity 
in the umbonal region; anterior profile with narrowly convex median region and 
long, flat, steep slopes to the margins. Umbonal region narrowly convex, the 
convexity carried to the median region where the surface becomes flattened. 
Median costella more elevated and stronger than those surrounding it, defining 
an indistinct fold. 
Pedicle interior with short, receding, and flaring dental plates; muscle area 
deeply impressed, extending a short distance anterior to the delthyrial cavity. 
Vascula media and reniform ovarian impressions not strongly impressed. 
Brachial valve evenly and gently convex in lateral profile with the greatest 
convexity at about the middle; anterior profile broadly convex, indented medianly 
by the sulcus; flanks bounding sulcus somewhat narrowly swollen; posterolateral 
slopes to the deflected cardinal extremities short and steep. 
Brachial interior with moderately elevated notothyrial platform, septumlike 
