778 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Measurements in mm.— 
Brachial Hinge 
Length length Midwidth width Thickness Height 
FUGlotypescs + + vacant et 8.8 7.4 12.3 12.3 23 4.2 
Paratype (117481a).. 8.6 7.4 11.9 13.0 2.4 3.9 
(11748Ic).. 7.5 6.3 10.8 11.4 2.0 3.4 
= (117481d).. 7.4 6.2 10.3 10.6 2.0 3.6 
FS (117481e).. 8.3 6.8 15.5 11.0 2.3 3.8 
Types.——Holotype: 117481b; figured paratypes: 117480a, 117481a,e,f; 
123258a-c; unfigured paratypes: 117480b-d, 117481c,d. 
Horizon and locality—Oranda formation in Virginia: 0.6 mile northwest of 
Linville Station, Broadway (15’) Quadrangle; along the railroad 4 mile west 
of Strasburg, Strasburg (15’) Quadrangle; just west of the junction of Virginia 
County Highways 617=910, and 777, 4 mile north of Green Mount Church, 
Broadway (15’) Quadrangle. 
Basal Martinsburg formation (part with Brongniartella=Salona) in Virginia: 
On Virginia County Highway 617=910, 0.15 mile north of Green Mount 
Church, 4 to 5 miles north of Harrisonburg, Broadway (15’) Quadrangle. 
Salona formation in Pennsylvania: On Fishing Creek, north edge of Salona, 
Lock Haven (15’) Quadrangle. 
Discussion.—This species suggests S. aequicostellata in its general configura- 
tion and ornamentation. The two species also occur in faunas that are obviously 
related. Sowerbyella cava is much more convex, is less transverse, and has more 
prominent cardinal extremities than S. aequicostellata. 
SOWERBYELLA COMPACTA Cooper, new species 
Plate 196, H, figures 51-59; plate 197, B, figures 11-24; plate 200, A, figures 1-6; 
plate 202, A, figures 1-8 
Shell about medium size for the genus, wider than long with the length equal 
to about two-thirds the width. Cardinal extremities slightly acute or approxi- 
mately rectangular, often auriculate. Lateral margins indented just anterior to 
the cardinal extremities, extending nearly straight or moderately obliquely to the 
anterolateral margins; anterior margin broadly curved. Anterior commissure 
rectimarginate to sulcate. Surface ornamented by costellae of nearly equal size, 
about 120 in number and 6 or 7 in 1 mm. at the front margin of an adult. In 
addition to these the costellae are provided with small crescentic beads and the 
interspaces are marked by fine concentric fila; on each side of the beak and just 
anterior to the posterior margin many specimens show 4 or 5 oblique wrinkles. 
Pedicle valve having a moderate convexity in lateral profile with the greatest 
convexity at about the middle; in anterior profile it forms a low arch highest 
in the middle and with the sides sloping moderately steeply to the margins. Beak 
inconspicuous, umbo narrowly swollen, produced forward as a more or less dis- 
tinct fold that may or may not reach the anterior margin. Valve full in mid- 
region, slopes to anterior and lateral margins moderately steep. Interarea slightly 
curved, moderately long and strongly apsacline. Pseudodeltidium small. 
