298 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
from O. divaricatus in having a shallower brachial sulcus, narrower and more 
elevated costae, and more numerous bifurcations of the costae. 
The interior of a pedicle valve is revealed in one specimen and shows a short 
and narrow delthyrial cavity with the usual orthoid musculature, but a low ridge 
extends anteriorly nearly to the middle of the valve. This ridge is much longer 
than the one in O. divaricatus. 
ORTHAMBONITES BLOUNTENSIS Cooper, new species 
Plate 35, C, figures 26-34 
Hebertella ? sp. Butts, Virginia Geol. Surv. Bull. 52, pt. 2, pl. 73, figs. 31-33, 1942. 
Shell small for the genus, wider than long; hinge forming the greatest width 
of the valves. Cardinal extremities slightly acute. Lateral margins gently curved 
and sloping slightly medially. Anterior margin broadly rounded. Anterior com- 
missure slightly sulcate. Ornamentation consisting of 17 or 18 broadly subangu- 
lar costae. 
Pedicle valve moderately convex with the greatest convexity in the swollen 
umbonal region. In anterior profile the convexity is moderate. Lateral slopes 
flat and moderately steep. Interarea curved, slightly apsacline. Beak incurved. 
Muscle area confined; median ridge thick and short. Interior with stout teeth, 
deep fossettes, and thick, short dental plates. Adductor track thickened. 
Brachial valve gently convex in lateral profile ; median sulcus narrow, occupy- 
ing one-third the width. Sulcus occupied by two costae. Flanks bounding sulcus 
gently swollen. Cardinal extremities depressed; slopes to extremities gentle, 
concave. Beak inconspicuous ; interarea moderately long. Interior having a nar- 
row notothyrial cavity, simple cardinal process and stout brachiophores. 
Measurements in mm.—Holotype, length 7.8, dorsal length 6.6, width 9.1, 
hinge width 9.8, thickness 4.5. 
Types.—Holotype: 109812h; figured paratypes: 109812a-c; unfigured para- 
types: 109812d-g,i,]. 
Horizon and locality—Arline formation in Tennessee: North side of wagon 
road in glade, { mile southeast of Friendsville; 100 yards southwest of Negro 
Cemetery, 4 mile northeast of Friendsville, Concord (T.V.A. 138-SW) Quad- 
rangle. 
Arline formation in Virginia: In the quarry just north of Marion, Marion 
(T.V.A. 218-SE) Quadrangle. 
Discussion.—This species is approximately intermediate between O. buttsi and 
O. bielsteini. The former is larger and wider and with more distant costae. In 
size and form O. bielsteini is somewhat larger but is more elongate and has a 
deeper and wider sulcus on the brachial valve. It differs from O. rotundiformis 
in its greater width and less prominent internal markings. 
ORTHAMBONITES BRACHIOPHORUS Cooper, new species 
Plate 36, E, figures 32-39 
Shell large, suggesting a Dinorthis in appearance, wider than long with obtuse 
or right angular cardinal extremities. Hinge as wide as the width at the middle or 
