PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 727 
sleevei are less strongly geniculated than the type brachial valve of Willard’s 
species. 
SOWERBYITES HAMI Cooper, new species 
Plate 181, C, figures 19-33 
Small for the genus, wider than long with the length about two-thirds the 
width at the hinge; cardinal extremities auriculate and forming an acute angle; 
sides gently rounded and sloping slightly toward the middle; anterior margin 
broadly rounded. Entire surface covered by very fine lamellae; larger costellae 
numbering about 2 to the millimeter at the anterior margin. Posterior margin 
with more or less well developed oblique wrinkles. 
Pedicle valve evenly and gently convex in lateral profile and with the maximum 
convexity at about the middle ; anterior profile broadly and gently convex. Umbo 
swollen, the swelling merging with that of the median region; flanks gently con- 
vex and sloping gently to the margins; anterior slope somewhat shorter and 
steeper than the lateral slopes. Interarea long and gently apsacline. 
Brachial valve most deeply concave in the median region from the umbo nearly 
to the front margin; flanks gently concave; cardinal extremities somewhat 
flattened. 
Interior of pedicle valve with little or no development of the callosities anterior 
to the diductor scars. Interior of brachial valve with low median septum and 
moderate development of the inner pair of septa; outer pair not well developed 
or absent. 
Measurements in mm.— 
Brachial Hinge 
Length length Midwidth width Thickness 
PROIOLYBE), vane st\- 05sec es oa ae 0.2 8.6 14.1 14.8 2.0 
Paratype CIIZ4A0OCy) Io.) ss ees 7.5 7.0 EY / 11.5 1.8 
Wd CET7AOGL) IRE. 8.6 7.9 11.5 12.4+- 1.9 
Types.—Holotype: 117400a ; figured paratypes: 117400b,d-f; unfigured para- 
types: 117400¢,g-j. 
Horizon and locality —Bromide formation (Pooleville member) in Oklahoma: 
From the shale beds immediately below the “Bromide dense” bed opposite the 
road leading to the abandoned village of Gilsonite; in the road cut on the east 
side of the section line road 1,300 feet south of the northwest corner of sec. 23, 
TS. KR: 3 E., Murray County. 
Discussion.—This species is characterized by its small size, moderately auricu- 
late cardinal extremities, poorly developed outer lateral septa inside the brachial 
valve, and poorly developed callosities at the anterior ends of the diductor scars 
of the pedicle valve. Small size distinguishes this species from other described 
species of Sowerbyites. The modest projections on the cardinal extremities are 
unlike those of young S. triseptatus which are often mucronate. Young stages 
of S. lamellosus, as indicated by growth varices, seem to have been more trans- 
verse shells than the adult S. ham. 
