336 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
outer marginal frill in the rock. The inner core thus obtained differs somewhat 
in proportions from the complete specimens. 
PRODUCTORTHIS AMERICANA Cooper, new species 
Plate 49, A, figures 1-4; plate 56, A, figures 1-5; plate 82, C, figure 12 
Productorthis sp., Butts, Virginia Geol. Surv. Bull. 52, pt. 2, p. 42, pl. 73, figs. 26-28, 1942. 
Large for the genus, length and width nearly equal. Hinge slightly narrower 
than the greatest width which is near the middle. Surface multicostellate and 
imbricate ; costellae numbering about 15 in 10 mm. at the front of the holotype; 
imbrications about I mm. apart. 
Pedicle valve strongly convex in lateral profile but flattened in about the mid- 
dle; strongly arched but medially flattened slightly in anterior profile. Median 
and anterior region swollen; lateral slopes steep and concave. Umbo swollen; 
beak incurved and almost touching the umbo of the brachial valve. Dental plates 
thick ; apical callosity large, excavated where the pedicle was attached. Gingly- 
moid joint deep. 
Brachial valve moderately convex in profile, median sulcus defined at the umbo 
but lost toward the front of the valve. Chilidium large, circular. 
Measurements in mm.— 
Hinge 
Length Width width Thickness 
Einictype 475.00stLw. Siiteed: B22 14.9 20.6 16.6 11.6 
Paratype (brachial valve 116887).. 11.4 14.1 13.8 1.5 
Types.—Holotype: 98184a; figured paratypes: 98184b, 116886b, 116887; un- 
figured paratype: 116886a. 
Horizon and locality—Arline formation in Virginia: Quarry on north side 
of Marion, Marion (T.V.A. 218-SE) Quadrangle. 
Botetourt formation in Virginia: North of Virginia Highway 114, 2.3 miles 
west of Montgomery-Roanoke County line, 12 miles northeast of Blacksburg, 
Montgomery County. 
Little Oak formation in Alabama: From a road cut on U. S. Highway 31, 4 
mile north of Pelham, Bessemer Iron District (15’) Quadrangle. 
Discussion.—This species is characterized by its strongly convex valves. It 
differs from P. agilera in its size and more closely crowded ornamentation as 
well as the shape of the valves. This is a very rare species, only four specimens 
having been found. 
The two specimens found in Catawba Valley, Va., and the brachial valve from 
the Little Oak limestone in Alabama are ornamented like the specimens from 
Marion, Va. They are not, however, as convex as the holotype. It appears cer- 
tain that the holotype has been somewhat shortened by compression on beak and 
anterior margin, thus shortening and thickening the specimen. 
Family HESPERONOMIIDAE Ulrich and Cooper, 1936 
Transverse Orthacea with flattish or shallow valves, orthoid muscle field in the 
pedicle valve, orthoid brachiophores, and a simple cardinal process. Pseudo- 
deltidium unknown, but chilidial plates or chilidium present. 
