776 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Types—Figured hypotypes: 117478a,b,f,g; unfigured hypotypes: 117478c-e. 
Horizon and locality—Wardell formation in Tennessee: Along the railroad 
just west of Liberty Hill, Dutch Valley (T.V.A. 154-SE) Quadrangle; 0.3 mile 
east of Mason’s store, Bristol (30’) Quadrangle; near the south end of Chicka- 
mauga Dam, 7 miles upstream from Chattanooga, East Chattanooga (T.V.A. 
112-SW) Quadrangle. 
Discussion.—This species is characterized by a subrectangular to subquadrate 
outline, fine costellae, and moderate convexity, and is like several others found 
in the Appalachian Valley. The ornamentation and proportions are like those 
of S. multicostellata, but the size attained is generally greater than that reached 
by the latter species. S. multicostellata is usually a much deeper shell. Sower- 
byella socialis approaches this species in form but is more strongly costel- 
late and has a more prominent development of the beaded costellae. Sower- 
byella lebanonensis does not attain the large size nor the somewhat quadrate 
form of S. aequistriata. 
SOWERBYELLA ANGULATA Cooper, new species 
Plate 206, A, figures 1-7 
Sowerbyella curdsvillensis Butrs (not Foerste), Alabama Geol. Surv., Special Rep. 14, 
p. 130, pl. 33, figs. 5, 6, 1926. 
Shell large for the genus, subrectangular in outline; hinge forming widest 
part; cardinal extremities acutely angular to auriculate; sides oblique; antero- 
lateral extremities broadly rounded; anterior margin nearly straight; costellae 
strong, not strongly differentiated in size at the front margin, 3 to 5 in a milli- 
meter at the front margin. A few strong wrinkles along the posterior margin. 
Pedicle valve strongly convex in lateral profile and with the maximum con- 
vexity in the median region; anterior profile strongly and broadly arched ; lateral 
slopes moderately long and steep; beak and umbo inconspicuous; median region 
strongly swollen; anterior slope convex and steep; median region marked by a 
narrow, indistinct median fold. Interarea long and strongly apsacline; ae | 
deltidium short. 
Brachial valve deeply concave in the median region, the concavity lessening 
laterally ; posterolateral extremities somewhat flattened. 
Pedicle interior with broad diductor scars bounded posterolaterally by mod- 
erately strong ridges. Brachial interior with 3 strong median septa, the median 
one almost as prominent as the lateral ones. Subperipheral rim not strongly 
thickened. 
Measurements in mm— 
Brachial Hinge  Thick- 
Length length Midwidth width ness Height 
1 (re (0) 5) eR Pe ea 12.5 11.3 18.2 22.6 3.5 5.4 
Paratype (71538)... ... 12.3 II.1 18.3 20.7 3.2 4.5 
C7TRIOCT ae caet 11.2 9.8 17.9 19.4 aE 4.6 
s CEITZAZOA) o enistos 10.6 9.5 16.9 20.5 3.0 4.5 
os CIUTTAFOD Nice wees ? Gags. es 19.0 ry ? 
