NO. 12 PERMIAN BRACHIOPODS FROM OREGON—COOPER 31 
by a strongly reticulate visceral disk, the deep sulcus originating just 
anterior to the visceral disk, and a long, prominent flange around the 
margin of the visceral disk. This species cannot be confused with the 
much larger P. elongata, new species, and differs from the other 
smaller, described marginiferas in having an inner flange in the 
brachial valve. 
Family DICTYOCLOSTIDAE Stehli, 1954 
Subfamily DicryocLostinaE Stehli, 1954 
AVONIA OREGONENSIS Cooper, new species 
Plate 2C, figures 13-24 
Shell large for the genus, subquadrate in outline with the width 
slightly exceeding the length; cardinal extremities nearly a right 
angle; lateral margins gently rounded; anterior margin broadly 
rounded. 
Pedicle valve strongly convex with a strongly incurved beak and 
strongly convex umbo. Outline of umbonal region forming approxi- 
mately a right angle. Median region inflated, with very steep slopes 
to the margins. Sulcus shallow, originating just anterior to the umbo, 
poorly defined, not always reaching the anterior margin. Hinge just 
slightly narrower than the maximum shell width which is located 
at about the middle. Ears ill defined. Surface marked by scattered 
pustules bearing long, slender spines; pustules continued into more 
or less long, rounded radial ridges most numerous and longest an- 
teriorly. 
Brachial valve about 20 percent shorter than the pedicle valve, and 
having a decidedly rectangular outline, strongly convex in profile, 
thus producing a thin visceral cavity; umbo deeply concave; fold 
poorly defined, anterior to umbo and extending to the front margin ; 
areas bounding fold deeply concave with the greatest concavity located 
at about the middle; ears well defined, deflected toward the pedicle 
valve and slightly concave. Surface marked by irregularly arranged, 
shallow, elongate pits corresponding to the spine-bearing pustules of 
the pedicle valve. 
Measurements in mm.—Holotype, length 24.6, width 29.1, thick- 
ness at middle 3.7, height from margin to point of maximum con- 
vexity of pedicle valve 15.2, surface measure 40+, length of brachial 
valve 20; paratype, U.S.N.M. 125322, length 19.0, width 25.4, thick- 
ness at middle 3.7, height 9.7, surface measure 30+, length of brachial 
valve 15.6. 
Types.—Holotype, U.S.N.M. 125323a; figured paratypes, U.S. 
