NO. 12 PERMIAN BRACHIOPODS FROM OREGON—COOPER 53 
which the adult has 6 costae on the fold. In the brachial valve the 
lateral intercalations in the sulcus are shorter than those in the 
Russian species which extend up to the umbo. 
STENOSCISMA BIPLICATOIDEUM Cooper, new species 
Plate 9E, figures 34-54 
Shell of about medium size for the genus, transversely pentagonal 
in outline, beak obtuse; sides narrowly rounded. Surface sparsely 
costate, the fold provided with 3 costae, the sulcus with 2, and the 
flanks with 2 distinct but short costae and a third obscure one. 
Pedicle valve moderately convex in lateral profile; umbonal region 
gently convex; sulcus originating at about the middle, shallow and 
occupying slightly less than half the width at the front. Tongue 
moderately long, narrowly rounded; costae in sulcus strongest near 
anterior margin. Flanks gently convex with gentle slopes to the 
margin, 
Brachial valve slightly deeper and more convex than the pedicle 
valve ; moderately convex and with the greatest convexity at the mid- 
dle in lateral profile ; fold originating about one-third the length from 
the dorsal beak, not strongly elevated, with costae fairly broad and 
separated by spaces narrower than the costae. Slopes of fold steep; 
flanks somewhat narrowly rounded and with steep slopes to the 
margins. 
Measurements in mm.—Holotype, length 17.0, brachial length 14.8, 
width 16.9, thickness 11.3. 
Types.—Holotype, U.S.N.M. 125382; figured paratypes, U.S.N.M. 
125383, 125384a-d; unfigured paratype, U.S.N.M. 125461. 
Localities —L8; P10; S47; U.O. 2205-5. 
Discussion.—This species differs from S. biplicata (Stuckenberg) 
as figured by Tschernyschew in its more transverse outline and the 
lesser development of the costae which in the American species are 
distinct only to about the middle of the valves. Furthermore, the 
sulcus is shallower and the fold somewhat narrower and lower than 
that of the Russian species. The most significant difference appears 
in the anterolateral angles which are narrower in the American form 
than in the Russian one and the tongue of the pedicle valve of the 
American species is more extended to give the valve a somewhat 
nasute appearance. 
