836 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Types.—Holotype: 117600c; figured paratypes: 117599a, 117600a; unfigured 
paratypes: 117599b, 117600b,d. 
Horizon and locality—Edinburg formation (Cyrtonotella zone) in Virginia: 
In ravine opposite switch, § mile east of Strasburg Junction, Strasburg (15’) 
Quadrangle. 
Discussion.—This is a large species characterized by considerable depth by 
virtue of a long trail. The visceral area is short, but the trail is exceptionally 
long and the sculpturing prominent. The species approaches D. magna in size 
and depth but differs in sculpture. 
DACTYLOGONIA SUBAEQUICOSTELLATA Cooper, new species 
Plate 217, J, figures 27-31; plate 2109, A, figure 1; plate 219, C, figures 6-9 
Shell about medium size to small for the genus, with the hinge narrower than 
the greatest shell width which is just anterior to the hinge. Lateral margins 
sloping gently toward the middle; anterior margin broadly rounded. Surface 
marked by narrow, elevated, rounded costellae of nearly equal size, spaced about 
17 in 5 mm. at the front. 
Pedicle valve gently convex, with the greatest convexity in the anterior half; 
flexed portion not prominent, point of flexure about 7 mm. anterior to the beak; 
umbonal region slightly swollen, the fullness continued anteriorly to the middle; 
on each side of this median elevation the valve is slightly flattened or sunken to 
the margins. Palintrope long, interarea flat, apsacline. 
Brachial valve with point of flexure 6 mm. anterior to the beak and at this 
point having its greatest concavity. The point of flexure on this valve is stronger 
than that on the pedicle valve; median region somewhat more concave than the 
surrounding areas and the region about the cardinal extremities flattened. Palin- 
trope unusually long and flat. Brachial interior with prominent adductor plates 
and small cardinal process. 
Measurements in mm.—Holotype, length 10, midwidth 12.9, hinge width 11.4, 
surface length 11, brachial valve length 8, thickness 2.2. 
Types—Holotype: 117602; figured paratypes: 117601b,c, 117603; unfigured 
paratype: 117601a. 
Horizon and locality—lLower Bromide (Mountain Lake member) in Okla- 
homa: McLish Ranch, sec. 24, T. 1 S., R. 7 E.; 2 miles southeast of McLish 
Ranch, 3 miles northwest of Bromide, Johnston County ; between Sylvan and Mill 
Creeks on west branch of Sycamore Creek, sec. 27, T. 3 S., R. 4 E., Carter 
County. 
Discussion.—This is a small and moderately concave species with fairly strong 
and crowded costellae. Its general form is like that of D. sculpturata but the 
size and general appearance suggest D. concentrica, which species, however, is 
flatter, somewhat smaller, and less strongly ornamentated. 
DACTYLOGONIA TRANSVERSA Cooper, new species 
Plate 217, C, figures 4, 5 
Shell considerably wider than long, with the hinge forming the widest part; 
sides short and slightly oblique ; anterior margin somewhat truncated to emargi- 
