66 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 134 
Measurements in mm. 
Length Width Thickness 
Flalotypes ss ett: Be. an he ae ees 8.6 6.3 6.0 
Paratype aCI25408)i sas so nene eee eee ho | 6.4 5.3 
Types.—Holotype, U.S.N.M. 125410; figured paratype, U.S.N.M. 
125408. 
Localities —S41 ; U.O. 2201-2, 2223-2. 
Discussion—This species has its closest affinities with R. nucleola 
(Kutorga) as redescribed by Tschernyschew. It is somewhat more 
elongate and slightly smaller than the Russian species and possesses 
a sulcate fold on the brachial valve which is not shown by Tscherny- 
schew’s specimens. It differs from R. merriami, new species, in its 
subnasute anterior, the more erect pedicle beak, and the less numerous 
costae on the anterior part of the valves. 
Family DIELASMATIDAE Schuchert and LeVene, 1929 
Subfamily DrELASMATINAE Schuchert, 1913 
DIELASMA? TRUNCATUM Cooper, new species 
Plate 10A, figures 1-6 
Shell small for the genus, pyriform in outline, with a moderately 
long posterior third; rounded lateral margins but truncated front. 
Beak incurved, foramen labiate. Pedicle valve most convex in the 
posterior half and particularly in the umbonal region. Median region 
slightly swollen and with gentle slopes to the lateral and front mar- 
gins. Brachial valve most convex in the posterior half; umbonal 
region swollen with moderate slopes to the posterolateral margins. 
Midregion gently convex. 
Measurements in mm.—Holotype, length 10.6, width 8.5, thickness 
6.2, length of brachial valve 8.8. 
Type.—Holotype, U.S.N.M. 125411. 
Locality.— S20. 
Discussion.—This species is represented by two specimens only, 
and it is not certain that the species belongs to Dielasma. It is differ- 
ent from all the other terebratuloids seen in the Oregon Permian in 
its truncated front margin and rectimarginate commissure. 
DIELASMA BREVICOSTATUM Cooper, new species 
Plate 12D, figures 32-41 
Of about medium size for the genus, longer than wide; valves 
unequally convex, the pedicle valve the deeper and more convex; 
