NO. 12 PERMIAN BRACHIOPODS FROM OREGON—COOPER AI 
about the same size as M. transversa and have a similar ornamen- 
tation, but the Chinese species is not so strongly geniculated nor 
does it have as strong a sulcus as the American species. 
Muirwoodia greenlandica Dunbar from Greenland is perhaps 
the nearest like the Oregon species but the extremely acute angle 
of geniculation separates these two species as it separates the 
Oregon shell from all others. 
Subfamily MARGINIFERINAE Stehli, 1954 
MARGINIFERA? BREVISULCATA Cooper, new species 
Plate 7B, figures 24-29 
Shell of about usual size for the genus, known only from the 
pedicle valve; length and width about equal; outline subquadrate. 
Sides and anterior margin gently rounded. Hinge equal to the 
greatest shell width. Surface with coarsely rugose visceral area 
with some reticulation, fine radial costellae on the trail and a few 
strong, radial plications. Spines few, but their pattern is difficult 
to determine. 
Visceral region somewhat swollen, equal in length to less than 
half the surface length of the valve; lateral profile of visceral area 
nearly flat except for the narrowly convex umbo; beak incurved 
over hinge. Slopes to cardinal extremities fairly steep. Cardinal 
extremities produced into small ears having an agle of about go°. 
Sulcus just barely perceptible at the anterior end of the visceral 
area just before the geniculated part of the valve. Angle of genic- 
ulation obtuse; trail gently convex in profile with moderately steep 
lateral slopes. Sulcus shallow, almost completely confined to the trail. 
Measurements in mm.—Holotype, surface length 23, length 13.5, 
length of visceral area 9.5, width at hinge 15.5, height 13.3. 
Types.—Holotype, U.S.N.M. 125363a; figured paratype, U.S. 
N.M. 125362; unfigured paratypes, U.S.N.M. 125363b-d. 
Localities —S30, S45, S4g. 
Discussion.—This species can be readily identified by its small 
size, short trail with sulcus confined to trail. It differs from Probo- 
lionia posteroreticulata, new species, in its shorter trail, less reticu- 
late visceral disk and shallower, shorter sulcus. No details of the 
interior of this species are known; consequently, the generic as- 
signment to Marginifera is queried. The exterior, however, is like 
that of all the other species described herein that are referred to 
Marginifera. 
