282 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
men small and posterior margin of slit overhanging the opening. Inside the 
pedicle valve the foramen enters the shell about 1.5 mm. from the posterior mar- 
gin and forms a tube that makes a ridge anterior to the umbonal chamber. A 
short ridge occurs anterior to the pedicle tube and in the umbonal chamber 
divides 2 muscle impressions. 
Brachial valve gently convex in the umbonal region but flattened to concave 
anteriorly ; posterior slope short, about I mm. in length in an adult shell, slightly 
concave and extended in about the same plane as the anterior part of the shell. 
Beak small, smooth and with a finely ornamented umbo; anterior slope convex 
and somewhat swollen in the posterior portion but becoming gently concave 
anteriorly ; posterolateral region reflected in a brachial direction and thus pro- 
ducing concave lateral slopes. Details of the interior not preserved. 
Measurements in mm.— 
Length Width Thickness 
Paratype (pedicle valve 109697c)............ 7.0 7.5 1.0? 
ot (brachial valve 109697e) .......... 11.0 12.0 ? 
Types.—Holotype: 109697b; figured paratypes: 109660a, 109697c,e-g, 
116806a-c,e,f,g ; unfigured paratypes: 109697a,d, 116806d,h,i. 
Horizon and locality.—FPratt Ferry formation in Alabama: 0.2 mile southeast 
of Pratt Ferry, Blocton (15’) Quadrangle. 
Discussion—This species is characterized by its depressed form, short and 
tear-shaped pedicle slit, and the anterior concavity of the brachial valve. In 
these respects it is quite unlike any of the species herein described. 
SCHIZOTRETA sp. 1 
Plate 19, G, figure 22 
This is a small species slightly more than 6 mm. in diameter and forming a 
high, irregular cone. The anterior and posterior slopes are nearly equal, but 
the latter is slightly shorter and steeper. The apex is bluntly rounded. The 
pedicle groove is long. The surface is marked by fine, even concentric lines. 
Figured specimen.—109650. 
Horizon and locality—Hogskin member of the Lincolnshire formation (upper 
30 feet) in Tennessee: 44 miles west-southwest of Thorn Hill, Avondale (T.V.A. 
162-SW) Quadrangle. 
Superfamily CRANIACEA Waagen, 1885 
Family CRANIIDAE Gray, 1840 
Usually calcareous shells cemented by the pedicle valve and with more or less 
conical brachial valve. 
EOCONULUS Cooper, new genus 
(Greek eos, early; conus, cone) 
Minute to small, misshapen cones with the apex on the posterior side; pos- 
terior margin nearly straight ; interior of brachial valve with a large, oval muscle 
