550 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
OXOPLECIA RECTA Cooper, new species 
Plate 104, A, figures 1-6 
Shell small for the genus, slightly wider than long; often somewhat distorted ; 
sides somewhat narrowly rounded ; anterior margin truncated ; widely uniplicate ; 
hinge moderately wide. Surface strongly costellate; costellae numbering about 
13; fold and sulcus with 5 to 8 costellae. Fila strong, numbering 5 to the milli- 
meter in the middle of the pedicle valve. 
Pedicle valve gently convex in lateral profile with the region between the mid- 
dle and the beak somewhat swollen; anterior profile gently and broadly convex ; 
beak long and pointed ; umbo somewhat flattened ; sulcus originating about 3 mm. 
anterior to the beak; sulcus broad and moderately deep, occupying more than 
half the width at the front margin. Tongue long and broadly rounded. Flanks 
bounding sulcus flattened and with little slope to the margins. Interarea long, 
curved, apsacline. 
Brachial valve moderately convex in lateral profile; strongly arched in an- 
terior profile: Fold wide but low and rounded; flanks bounding fold gently 
inflated but with moderate lateral slopes. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
Holotype 2020. A. Pee II.9 10.3 13.4 8.8 Fi 
Paratype) (207124) 21a. ik 12.6 10.6 13.9 9.2 7.8 
Types.—Holotype: 110849a; figured paratype: 117124; unfigured paratypes: 
110849b,c. 
Horizon and locality—Lincolnshire formation (Hogskin member), in Ten- 
nessee: On Sally Cleveland Farm, 3 mile southwest of Washburn, Dutch Val- 
ley (T.V.A. 154-SE) Quadrangle; 0.4 mile northeast of Red Hill, 44 miles west- 
southwest of Thorn Hill, Avondale (T.V.A. 162-SW) Quadrangle; school at 
Chesney, 2 miles northeast of Luttrell, Luttrell (T. V. A. 155-NW) Quadrangle. 
Lincolnshire formation in Tennessee: 4 mile north of Eidson, Kyles Ford 
(T.V.A. 170-SE) Quadrangle. 
Discussion.—This species is most similar to O. planiventra. The differences 
between them are discussed under that species. 
OXOPLECIA SIMULATRIX (Bassler) 
Plate 1o1, A, figures 1-10; plate 1o1, B, figures 11-15 
Triplecia (Cliftonia) simulatrix BAssLer, Cambrian and Ordovician: Maryland Geol. Surv., 
p. 266, pl. 40, figs. 11-13, 1919. 
Shell of large size, transversely elliptical in outline with the length equal to 
about three-fourths the width. Lateral margins narrowly rounded, anterior mar- 
gin truncated. Width of hinge slightly more than half the shell width. Surface 
strongly multicostellate, with the sulcus occupied by 6 to g costellae and the fold 
by 7 to 10. Flanks marked by 15 to 18 low, rounded costellae separated by 
