296 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Types —Holotype: 116866c; figured paratypes: 109799a-e, 116866a,e,f; un- 
figured paratypes: 116866b,d,g. 
Horizon and locality —Chatham Hill formation in Virginia: On the Grayson 
Farm, 4 miles southwest of Bland, Bland County; north slope of Walker Moun- 
tain, 1.2 miles S. 31° E. of Sharon Springs, Burkes Garden (15’) Quadrangle. 
Discussion.—This species has some of the external expression of O. rotundi- 
formis but differs in having less costae, lesser convexity of the pedicle valve, 
somewhat more convex brachial valve, and a more strongly apsacline interarea. 
This species is common in the lower Chatham Hill near Sharon Springs. 
CRTHAMBONITES BIELSTEINI Cooper, new species 
Plate 36, B, figures 9-18 
Shell of about medium size for the genus, longitudinally semielliptical in out- 
line ; length and width equal, or wider than long. Hinge slightly narrower than 
the greatest shell width which is at about the middle. Lateral margins gently 
rounded; anterior margin somewhat narrowly rounded. Surface costate, costae 
15 to 18 in number, subangular and with interspaces narrower than the width 
of the costae. 
Pedicle valve unevenly convex in lateral profile with the greatest convexity 
in the posterior half, the front half somewhat flattened. Anterior profile with 
narrowly rounded summit and steeply sloping sides. Umbo subcarinate and pre- 
umbonal region swollen and produced anteriorly as a low fold which becomes 
nearly obsolete at the front margin. Flanks flat in profile with moderately steep 
slopes. Anterior slope not so steep as the lateral ones. Interarea short, curved, 
gently apsacline. 
Brachial valve with gently convex lateral profile but with the greatest curva- 
ture in the umbonal region. Anterior profile a slightly convex arch slightly de- 
pressed medially. Sulcus originating on the umbo, expanding anteriorly, shallow 
throughout its extent and occupying about 4 mm. at the front of the valve. Flanks 
very gently convex. Cardinal extremities depressed noticeably. Interarea short, 
anacline. 
Measurements in mm.— 
Hinge 
Length Width width Thickness 
TOU oer cree « paacetieaselnaeced 11.5 11.8 9.3 5.6 
Figured specimen (109801) ...... 10.9 12.1 10.0 ? 
Types.—Holotype : 1098038 ; figured paratype: 109803b; unfigured paratypes : 
109803¢,d ; figured specimens: 109845a, 109801. 
Horizon and locality—Martinsburg formation (Salona equivalent) in Vir- 
ginia: About 14 miles north of Staunton. 
Oranda formation in Virginia: 0.6 mile northwest of Linville Station, Broad- 
way (15’) Quadrangle. 
Benbolt formation in Virginia : + mile east of Speers Ferry, Clinchport (T.V.A. 
188-NW) Quadrangle. 
