360 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
the front margin where the sulcus occupies nearly half the width; sides bound- 
ing sulcus nearly flat; posterolateral extremities deflected slightly toward the 
pedicle valve. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
ETIGIGEY Pei? s.ctlegs sudiyes:< 13.9+ 12.0 14.8 13.9 6.6 
Paratype (97508).... 15.9 13:2 16.5 14.2 7.0-+ 
Types.—Holotype: 116927a; figured paratype: 97598; unfigured paratype: 
116927b. 
Horizon and locality—Oranda formation in Virginia: 4 mile north-northwest 
of Green Mount Church; Broadway (15’) Quadrangle. 
Discussion—This species is characterized by its slender form, subcircular 
outline and steeply apsacline pedicle interarea. It is less convex, more slender in 
outline, and somewhat more circular in outline than H. australis to which it has 
some resemblance. 
HESPERORTHIS sp. 1 
Plate 54, F, figure 41 
Represented by two specimens from the Botetourt formation in Virginia ex- 
posed at the junction of Virginia Highways 311 and 114, 4 mile southwest of 
Catawba, Salem (15’) Quadrangle. One specimen is crushed but shows both 
valves. The exterior is marked by about 25 narrowly rounded costae. The 
brachial sulcus is narrow, shallow, and inconspicuous. Scarcely any trace of 
folding is exhibited on the pedicle valve. The interarea is curved, apsacline, but 
not strongly so. 
The second specimen is a cast of the pedicle interior showing strong dental 
plates but a small muscle field. The lack of marked folding sets this shell apart 
from all others described herein, but the specimens are too poor for further 
elaboration. 
Figured specimen.—109972. 
HESPERORTHIS sp. 2 
Plate 50, C, figures 8-13 
A very well preserved specimen of Hesperorthis was taken near the middle 
of the Edinburg formation (Nidulites zone) in Virginia, along Tumbling Run 
about 14 miles southwest of Strasburg, Strasburg (15’) Quadrangle. It closely 
resembles the type specimen of H. disparilis now assigned to H. tricenaria, but 
it differs from that species in details of the ornamentation, showing it to be a 
different species. The specimen is probably the young of a Hesperorthis which 
has not yet been seen in adult form. 
Figured specimen.—1 16926. 
