324 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
est convexity in the median region; umbonal and posteromedian areas swollen ; 
slopes to cardinal extremities steep, concave. Anterior and anterolateral slopes 
moderately steep. Interarea short, strongly curved, anacline; delthyrium wide. 
Brachial valve gently concave with the maximum cavity at about the middle; 
sulcus originating almost at the posterior margin, thus producing a concave umbo. 
Sulcus wide but shallow, disappearing anteriorly near the front margin. Flanks 
flat to very gently convex. Cardinal extremities flattened. Interarea short; 
chilidial plates small. Interior with short, wide, and stout median ridge. Cardi- 
nal process erect, small; brachiophores short. 
Measurements in mm.—Holotype, length 24.5, brachial length 22.1, width 28.8, 
hinge width 27.8, thickness 5.2. 
Types.—Holotype: 109860a ; figured paratype: 109860b ; unfigured paratype: 
109860c. 
Horizon and locality—Edinburg formation (Cyrtonotella zone) in Virginia: 
Shaly beds just above the quarry 4 mile east of Strasburg Junction; ravine at 
switch 4 mile east of Strasburg Junction; Strasburg (15’) Quadrangle. 
Discussion—This species differs from C. virginiensis Butts by its proportion- 
ately greater length in relation to width, less elevated and less crowded costellae, 
and more elongate interarea of the pedicle valve. 
CYRTONOTELLA SUBQUADRATA Cooper, new species 
Plate 4o, B, figure 11; plate 82, E, figures 21, 22 
Shell large for the genus, subquadrate in outline; cardinal extremities acute 
in the young, obtuse in the adult ; sides gently rounded ; anterior broadly rounded ; 
surface multicostellate, costellae narrowly rounded but separated by striae wider 
than the costellae ; about 6 costellae in 5 mm. at the anterior margin. 
Pedicle valve moderately convex in lateral profile with the greatest convexity 
in the posterior half ; umbo strongly curved; anterior profile broadly convex with 
long and flat lateral slopes to the margins. Anterior slope long and rounded. 
Umbo swollen; median region swollen and somewhat inflated to the anterior 
margin. Umbonal slopes long, gently concave. 
Brachial valve gently concave in lateral profile with the greatest concavity in 
the median region; umbo sulcate, sulcus shallow but deepening and widening 
anteriorly to a point somewhat anterior to the middle where the deepest point is 
reached ; near the anterior margin the shell is somewhat elevated and the sulcus 
becomes obsolete ; flanks bounding sulcus nearly flat. 
Measurements in mm.—Holotype, length 23.6, brachial length 22.3, width 
28.9, hinge width 22.6, thickness 7.8. 
Types.—Holotype: 111803; figured paratype: 116895. 
Horizon and locality——Benbolt formation (Echinosphaerites beds) in Vir- 
ginia: On the west slope of the hill 4 mile east of Cedar Point School, Hilton 
(T.V.A. 197-NW) Quadrangle. 
Benbolt formation in Tennessee: On the north side of the road, 1.1 miles 
northeast of Lee Valley, Lee Valley (T.V.A. 171-NW) Quadrangle. 
