PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 461 
tion of a distinct fold; flanks moderately swollen with moderately wide but steep 
slopes. Interior with short, stout brachiophores and strong, well-defined support- 
ing plates. Median ridge short, narrow. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
Holotype (pedicle valve)........... 13.0 ? 16.0 12.9 5.0 
Paratype ( “ SS PTOSRSM)!. a5 LEST ? 15.8 II.4 4.7 
a (brachial valve 110582n).. =? 12.3 15.7 12.1 4.6 
Types——Holotypes: 110582b; figured paratypes: 110582a,d,n; unfigured 
paratypes : 110582c,e-m. 
Horizon and locality—Macy formation (Zell member) in Missouri: Along 
the old road 1 mile northwest of the Chicago Summer School Camp, NW4SW4 
sec. 32, 1. 37 N., R.9 E., Ste.,Genevieve County. 
Discussion—This species is suggestive of D. tennesseensis but is somewhat 
more rounded than that species. It is also slightly more strongly costellate, has a 
narrower pedicle sulcus and somewhat less abrupt brachial wave in the anterior 
commissure. 
DOLEROIDES OKLAHOMENSIS Cooper, new species 
Plate 92, A, figures 1-4; plate 96, A, figures 1-21 
Shell about medium size for the genus, wider than long with the hinge nar- 
rower than the greatest shell width which is located slightly anterior to the 
middle. Cardinal extremities obtuse, posterolateral margins straight, directed 
obliquely away from the midline; anterolateral extremities narrowly rounded, 
anterior margin gently rounded to nearly straight. Anterior commissure recti- 
marginate or faintly uniplicate or sulcate. Multicostellate, costellae unequal in 
size and appearing in about 4 generations and with a few scattered ones of larger 
size; about 17 in 5 mm. at the front margin. On the anterolateral extremities 
a tendency to fasciculation of the costellae is prominent. Costellae and interspaces 
marked by fine concentric fila. 
Pedicle valve most convex in the posterior half when viewed in profile; an- 
terior half somewhat flattened in the same view. Umbonal and median regions 
swollen and convex with moderately steep slopes to the cardinal extremities but 
less steep slopes to the lateral margins; anterior slope gentle. Interarea nearly 
procline, curved near the beak. 
Brachial valve evenly and gently convex in lateral profile, broadly and gently 
convex in anterior profile. Sulcus originating at the umbo and extending as a 
narrow, Shallow depression to the middle of the valve and from thence appear- 
ing as a wide, shallow or flattened space not affecting the anterior margin. Flanks 
bounding sulcus slightly swollen; umbonal slopes moderately steep. Interarea 
short, orthocline. 
Pedicle interior with well-developed dental plates, elongate muscle field with 
long slender diductor scars; pallial trunks not well developed. Notothyrial cavity 
wide ; cardinal process stout ; brachiophores stout ; brachiophore supports low and 
wide. 
