252 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
40° to 60°. Beak curved posteriorly above the pseudointerarea which is narrow 
and one-half the width of the valve. Anterior side of cone strongly convex. 
Lateral surfaces strongly rounded. Surface marked by fine concentric lines. 
Brachial valve slightly elliptical, wider than long; posterior margin narrow, 
nearly straight. Lateral and front margins strongly rounded. Lateral profile 
unequally convex with a moderately convex umbo and posterior third; con- 
vexity decreasing anteriorly to about two-thirds the length from the beak, where 
the valve is flattened. From here to the front margin it is gently concave. Beak 
marginal, protruding slightly posterior to the posterior margin. Median septum 
extending to middle. 
Measurements in mm.— 
i Length Width Height 
Holotype (pedicle valve) ................000- 5.0 6.8 6.3 
Paratype (brachial valve 109734d)............ 8.0 7.8 ? 
Types.—Holotype: 109734b; figured paratypes: 109734c,e, 117968a-c; un- 
figured paratypes: 109734a,d,f-m. 
Horizon and locality.—Pratt Ferry formation (lower 3 feet) in Alabama: 0.2 
mile southeast of Pratt Ferry, Blocton (15’) Quadrangle. 
Discussion.—See Conotreta magna. 
CONOTRETA MAGNA Cooper, new species 
Plate 16, D, figures 11-17 
Shell large for the genus, resembling C. gigantea but dull black in color; 
pedicle valve forming an elongated cone; brachial valve nearly flat; surface 
marked by crowded concentric undulations and fine lines of growth. 
Pedicle valve with the thickness or height of the cone about equal to the width; 
lateral profile conical with the posterior side flattened and slightly concave; an- 
terior side moderately convex; anterior profile conical with very slightly convex 
sides ; apical angle about 40°. Pseudointerarea narrow, measuring about 24 mm. 
Intertrough shallow. Valve margin forming a circle. Interior unknown. 
Brachial valve nearly circular, very slightly convex in profile with the um- 
bonal region forming the most convex part; anterior half flattened; hinge line 
narrow ; median ridge extending at least to the middle. 
Measurements in mm.— 
Length Width Thickness 
Holotype (pedicle valve) .........leshwe ceeds 7.0 7.4 7.8 
Paratype (brachial valve 109732a)...........-. 5.7 6.2 ? 
Types.—Holotype: 109733; figured paratypes: 109732a,b; unfigured para- 
type: 109732c. 
Horizon and locality—Whitesburg formation in Bulls Gap (T.V.A. 171-SE) 
Quadrangle, in Tennessee: 2 miles west of Bulls Gap Station, 14 miles west of 
Bulls Gap, and 24 miles southeast of Whitesburg. 
Discussion—This species is most suggestive of C. gigantea but differs in its 
proportions and other details. Conotreta magna has a smaller apical angle than 
