Q22 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Measurements in mm.— 
Brachial Hinge 
Length length Midwidth width Thickness Height 
FAQIGUS PE... 0 a oeeeet ats 16.1 14.4 20.5 20.2-++ 3.9 7.4 
Paratype (117844b)..... 16.5 14.8 21.0 20.0 4.2 6.9 
4 (117844d)..... 13.0 12.0 16.6 16.8 32 5.0 
“5 (TI7845a) 20.2 15.8 14.6 19.1 20.2 2.8 5.1 
= (117843b)..... 14.5 13.3 18.0 17.3 2.6 5.0 
: (117843c) .'.... 13.8 17 Lig: ? 3.0 5.6 
« (ua7B40a)E s8 11.8 11.2 16.7 20.4 1.6 2.5 
‘ (117846c)..... 14.1 13.1 18.3 17.5 3.0 5.8 
ie (TI7SA5a) steht 19.9 18.3 27 2 23.7 4.4 10.0 
ie (117842)... hse 17.4 16.4 22.5 26.1 2.4 5.7 
Types.—Holotype: 1178442 ; figured paratypes : 98226a,b, 117843d, 117846a-d, 
123276a; wunfigured paratypes: 98226c-h, 117842, 117843a-c, 117844b-d, 
117845a-f, 117846e, 123276b. 
Horizon and locality—Wardell formation and Wardell part of Dryden forma- 
tion in Tennessee: Lloyd Carter’s barn, 0.8 mile by road northeast of Rye Cove 
School ; second road cut west of L. McDavid’s house, 1 mile west of Rye Cove; 
Clinchport (T.V.A. 188-NW) Quadrangle. 
Discussion.—This is a variable species ranging from extremely transverse 
shells to ones that are nearly square in outline. This species is smaller, wider, 
and more convex then O. speciosa and formosa. It is larger and more convex 
than O. parvula and is shaped and ornamented differently from O. bellula. Be- 
sides being very differently shaped, it is more convex and also more deeply con- 
cave than O. minnesotensis to which it has mistakenly been referred. The shell 
geniculates nearer the beak than in O. varia. 
OPIKINA VARIA Cooper, new species 
Plate 240, A, figures 1-7 
Rafinesquina aff. minnesotensis Butts (not Winchell), Alabama Geol. Surv., Special Rep. 14, 
p. 126, pl. 31, figs. 23, 24, 1926. 
Shell small for the genus, subquadrate to subrectangular in outline, slightly 
wider than long; sides gently rounded, subparallel; anterior margin broadly 
rounded. Hinge generally equal to or less than the width at the middle. Costellae 
well differentiated, 2 of the larger size in 1 mm. at the front margin. Larger 
costellae separated by 2 to 4 of the finer ones. 
Pedicle valve unevenly convex in lateral profile, with the maximum convexity 
anterior to the middle; anterior profile moderately domed ; geniculation occurring 
about II mm. anterior to the beak; angle of geniculation 115°; visceral region 
varying in lateral profile from nearly flat to moderately convex; anterior slope 
gently convex, short and steep; sides with short and steep slopes; interior with 
muscle field to about the middle of the valve. 
Brachial valve gently concave in the visceral region which extends for about 
3 the length ; deepest part anterior to middle; sides and anterior margin narrow 
and abruptly bent in the direction of the brachial valve. 
