916 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Horizon and locality—Benbolt formation in Virginia: 5 miles northwest of 
Wytheville, Wythe County; 4 mile southeast of Green Valley Church, 3 miles 
southwest of Lebanon, Brumley (T.V.A. 205-SE) Quadrangle. 
Discussion—For comparison with O. bellula and O. dorsatiformis see those 
species. 
OPIKINA ? PLANULATA Cooper, new species 
Plate 247, A, figures 1-4 
Shell large for the genus, subquadrate in outline, length slightly less than the 
width ; hinge forming the widest part; sides oblique; anterior margin somewhat 
narrowly rounded; costellae on pedicle valve numbering 3 to the millimeter at 
the front margin, 2 large and I small; brachial valve with somewhat finer cos- 
tellae, usually 4 to the millimeter of subequal costellae. 
Pedicle valve gently convex in lateral profile with the anterior profile broadly 
convex ; umbo narrowly swollen to form a short fold; umbonal slopes descend- 
ing gently to the cardinal extremities; median region gently swollen; anterior 
slope gently convex but steeper than the longer lateral slopes. Muscle field not 
quite reaching the middle. 
Brachial valve gently concave in the posterior region and reaching its deepest 
part anterior to the middle ; cardinal extremities flattened. Sides gently deflected 
toward the brachial valve; anterior margin fairly strongly bent in the direction 
of the brachial valve. 
Measurements in mm.— 
Brachial Hinge Thick- Height 
Length length Midwidth width ness 
Holotype (pedicle valve) .......... 2 ry 26.9 32.2 ? acc 
Paratype (brachial valve 117824b).. ? 28.8 34.4 35.5 ? ? 
Types.—Holotype: 117824a; figured paratypes: 117824b-d; unfigured para- 
types: 117824e-g. 
Horizon and locality.—Pierce formation in Tennessee: At old Pierce Mill 
site on Stone River at bridge on Tennessee Highway Io, just south of Walterhill, 
7% miles north-northeast of Murfreesboro, Rutherford County. 
Discussion—This species is questionably referred to Opikina. It has some 
features that suggest Macrocoelia such as the large size and low convexity, but 
the small muscle scar in the pedicle valve is not characteristic of Macrocoelia. A 
small brachial interior is more suggestive of Opikina. If it belongs to that genus, 
it is the least convex of the species discussed herein. If it belongs to Macrocoelia, 
it is suggestive of M. bella but is differently shaped and not quite so convex. 
OPIKINA PULCHELLA Cooper, new species 
Plate 244, B, figures 10-16; plate 246, B, figures 3, 4 
Shell small for the genus, longer than wide, and with the hinge forming the 
widest part. Sides gently rounded, oblique; anterior margin narrowly rounded 
to subnasute ; cardinal extremities nearly a nent angle. Costellate, 4 to 5 costel- 
lae in I mm. at the front margin. 
