gio SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, 127 
Measurements in mm.— 
Brachial Hinge 
Length length Midwidth width Thickness Height 
Holotype c:.cdS eh Wie 19.3 18.0 22.5 23.9 3.5 6.3 
Paratype (123272c)..... 13.0 12.3 14.5 16.8 £7 2.9 
“ (117800). «..,2%, 20.0 18.0 23.1 22.4 4.7 8.0 
- (II7S10c).. «2. 19.1 17.7 21.9 20.8 3.9 6.3 
CIV7OUIAD ons ss 18.9 17.3 22.8 20.9 3.9 6.2 
43 (117811d)..... 15.0 14.2 17.6 17.2 2.5 3.8 
Types.—Holotype: 123272a; figured paratypes: 117808, 123269b, 123270a, 
123271a, 123272b; unfigured paratypes: 117809, 117810a-d, 117811a-d,e,f, 
117813, 123272c-f. 
Horizon and locality—Bromide formation (Pooleville member-O-roplecia 
gouldi zone) in Oklahoma: At Rock Crossing, center sec. 35, T.5 S., R. 1 E., 
Criner Hills, 4 mile west of U. S. Highway 77, sec. 25, T. 2 S., R. 1 E.; West 
Spring Creek, 3 miles east of Pooleville; NW4 sec. 26, T. 5 S., R. 1 E., Criner 
Hills ; Carter County. Quarry on the east side of Oklahoma Highway 18, center 
SW5 sec. 12, T. 1 S., R. 3 E., 2 miles south of Sulphur, Murray County; Spring 
Creek, N4 sec. 17, T. 2 S., R. 1 W., Murray County. 
Discussion.—This species is most like O. speciosa of all those described herein 
but differs in being less convex, in having more pronounced ears, and in having 
a shorter anterior trail. 
OPIKINA GLABELLA Cooper, new species 
Plate 230, A, figures 1-7; plate 247, C, figures 7-10 
Medium sized for the genus, wider than long; subrectangular in outline and 
with the hinge equal to or greater than the midwidth; sides gently rounded; 
anterior margin broadly rounded; surface with well-differentiated costellae, 5 to 
the millimeter at the front margin. Oblique wrinkles present on posterior margin. 
Pedicle valve evenly and strongly convex in lateral profile, no marked posi- 
tion of geniculation detectable; maximum convexity at or near the middle; an- 
terior profile strongly domed; beak prominent; umbo narrowly swollen and 
forming a small eminence anterior to the beak; median region strongly swollen ; 
sides and anterior slope steep. Interarea short. Interior unknown. 
Brachial valve fairly deeply concave, the greatest depth just anterior to the 
middle ; posterior half gently concave but the umbo and median region marked 
by a shallow sulcus. Sides moderately deflected but anterior margin strongly 
deflected toward the brachial valve. 
Measurements in mm.—Holotype, length 15.9, brachial length 15.0, midwidth 
17.7?, hinge width 16.9?, thickness 3.9, height 6.5. 
Types.—Holotype: 123267b; figured paratype: 123267a; unfigured paratype: 
123267¢c. 
Horizon and locality—Arline formation (upper) in Tennessee: On north 
side of old road in glade, 4 mile southeast of Friendsville, Concord (T.V.A. 
138-SW) Quadrangle. 
Discussion—This species is characterized by having its length and width 
