250 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Discussion.—This species is suggestive of C. gigantea, but it is generally a 
thicker shell, more slender, and with a smaller apical angle. It is an uncommon 
species in the insoluble residues from Pratt Ferry. 
CONOTRETA ? CONCENTRICA Cooper, new species 
Plate 18, C, figure 22 
Shell fairly large for the genus, represented by the pedicle valve only. Nearly 
symmetrically conical in profile with the apex subcentral; lateral profile with 
gently convex anterior slope and long steep, nearly flat posterior slope. Anterior 
profile conical with gently convex sides; apical angle obtuse. Foramen apical, 
minute. Apical half of shell marked by very fine concentric growth lines ; anterior 
half marked by strong, regular, elevated concentric ridges which do not extend 
over the pseudointerarea ; pseudointerarea broad and flat ; intertrough not clearly 
discernible. Interior without visible structures. Accurate measurements not 
possible. 
Type.—Holotype: 116814. 
Horizon and locality.—Lower 3 feet of the Pratt Ferry formation in Alabama: 
0.2 mile southeast of Pratt Ferry, Blocton (15’) Quadrangle. 
Discussion—This is the only species assigned to Conotreta which has strong 
marginal corrugations. The ornamentation thus suggests that of Scaphelasma, 
but the other features are quite different. It was not possible to ascertain the 
interior structure; no apical callosity like that of Conotreta was seen, and it is 
probable that this specimen represents a new genus. Until the brachial valve is 
known, it is not possible to understand the true relationships of the genus. 
CONOTRETA CUSPIDATA Cooper, new species 
Plate 16, B, figures 4-7 
Shell of moderate size; pedicle valve nearly circular in outline, lateral profile 
a narrow wedge. Pseudointerarea triangular, occupying a little more than one- 
third the width. Apical angle 60°; lateral angle 50°. Beak bent very slightly 
posteriorly. Surface ornamented by concentric, low undulations and fine con- 
centric lines. 
Brachial valve almost circular, but with the posterolateral margins somewhat 
shouldered; very gently convex in lateral profile. Median sulcus shallow and 
narrow, practically obsolete at the front margin. 
Measurements in mm.—Pedicle valve (109716a), posterior slope 2.5, anterior 
slope 3.3, width at base of cone 3.1. Brachial valve (109716b), length 3.0, width 
3:8. 
Types.—Holotype: 109716a; paratype: 109716b. 
Horizon and locality—Effna formation in Virginia: Porterfield Quarry, 5 
miles east of Saltville, Maccrady (T.V.A. 218-NW) Quadrangle. 
Discussion.—See Spondylotreta? declivis. 
