258 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
TORYNELASMA TORYNIFERUM Cooper, new species 
Plate 9, C, figures 9, 10; plate 18, E, figures 28-36; plate 28, E, figures 13-16 
Shell small, acutely and fairly symmetrically conical in profile; color shiny 
straw-yellow ; surface marked by fine, concentric lines. 
Pedicle valve fairly symmetrically conical in both profiles; margins almost 
roundly elliptical, strongly oblique to the shell axis; posterior side convex in 
cross section and thus without a conspicuous pseudointerarea; intertrough in- 
conspicuous ; apical angle 35 to 40°. 
Brachial valve roundly elliptical in outline; fairly strongly convex in lateral 
profile; broadly convex in anterior profile; beak small, slightly protruberant. 
Brachial interior with shelflike area, short but wide, extending anteriorly from 
the hinge over the interior; spoon-shaped plate narrow posteriorly but widening 
anteriorly to reach its widest point near the anterior end; median septum crested 
anteriorly and reaching its highest point at its anterior extremity ; median septum 
protruding slightly anterior to the anterior end of the spoonlike plate; spoon- 
shaped plate characterized by a deep median area with a rim on each side set 
off by a longitudinal suture line. 
Measurements in mm.— 
Height 
Length Width Thickness aeataaa 
Holotype (brachial valve) ........ rit 1.6 0.4 0.75 
Paratype (pedicle valve 116824a).. 1.3 1.8 2.5 ? 
Types.—Holotype: 116825c; figured paratypes: 116824a-c, 116825d-f; un- 
figured paratypes: 116824d, 116825a,b,g,h. 
Horizon and locality—Pratt Ferry formation (lower 3 feet) in Alabama: 
0.2 mile southeast of Pratt Ferry, Blocton (15’) Quadrangle. 
Discussion—This species is characterized by its fairly large size, the acutely 
pointed pedicle valve, and the deep, spoon-shaped plate supported for its entire 
length by the median septum. Besides its size, it differs in the latter respect from 
T. minor in which the anterior end of the spoon-shaped plate is free and the 
anterior end of the median septum forms a free point. 
RHYSOTRETA Cooper, new genus 
(Greek rhysos, wrinkled; tretos, opening) 
Shells small, thick, conical in outline; surface of both valves marked by regu- 
lar, closely spaced, concentric elevated rings. 
Pedicle valve conical in profile; posterior side flattened to form a pseudointer- 
area ; intertrough usually narrow, shallow. Foramen large, tear-shaped, with the 
apex of the tear at the valve apex; foramen located just posterior to the apex. 
Brachial valve nearly flat in both profiles but deeply concave anterior to the 
umbo and in the median part of the valve; anterior rim often convex. 
Pedicle interior without any trace of muscle marks or septa. Brachial interior 
with a strong median septum arising a short distance anterior to the posterior 
margin and extending to the front margin. Septum highest at its anterior end. 
