NO. 12 PERMIAN BRACHIOPODS FROM OREGON—COOPER 39 
costellae in 5 mm. Brachial valve with concentric lamellae crowded 
anteriorly. 
Pedicle valve with profile unequally convex, anterior half gently 
convex but posterior half almost semicircular. Anterior profile mod- 
erately rounded. Beak protruding over hinge; umbo somewhat swol- 
len and the costellae cancellated by a few low rugae. Median region 
swollen and tumid, fold low, indistinct, and narrow, occupying the 
front half. Lateral slopes moderately steep. 
Brachial valve moderately concave, most concave in the midregion. 
Interior unknown. 
Measurements in mm. 
Surface 
length Length Width Height 
OL OEVDC IS erT ae ore aie alia araus ceoene eres 30.0 15.0 17.0? 10.0 
Patatype (125351). xcs. voce wae 26.0 15.0 14.0 10.0 
Paratype, (i25460) 29553. 05.4.06 ? 7.0 10.4 ? 
Types.—Holotype, U.S.N.M. 125361 ; figured paratypes, U.S.N.M. 
125351, 125360, 125466, 125534, 125535. 
Localities —L8 ; P12; S41, S43, S46, S50, S87, S103 ; U.O. 2201-1, 
2201-2, 2204-1, 2204-2, 2207, 2207-2, 2215-1, 2216-1. 
Discussion——No American species like A. minor are known. Cer- 
tain small linoproductids such as L. waagenianus Girty are known to 
be generically distinct from Amidanthus and are thus excluded. How- 
ever, one Russian species, A. aagardi (Toula), is similar to the 
Oregon species. The Russian form, however, is larger and less 
strongly convex than the American species. The costellae of the 
Oregon species are stronger than those of the Russian form. 
MUIRWOODIA TRANSVERSA Cooper, new species 
Plate 5A, figures 1-13 
Shell fairly large, width almost twice the length; cardinal extremi- 
ties acutely angular; lateral margins nearly straight but oblique; 
front margin bilobed. Shell strongly geniculated 16 mm. from the 
beak; angle of geniculation 65° to 75°. Geniculated trail slightly 
longer than the visceral region. Surface costellate, with about 8 
costellae in the space of 5 mm. at the point of geniculation and at 
the front margin. 
Pedicle valve with visceral region gently convex in lateral profile, 
geniculated area narrowly rounded; trail gently convex in profile, 
slightly more so than the visceral area. Sulcus originating about 
