254 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
declivis. It differs from C. cuspidata in having a less sharply pointed beak and a 
larger apical angle. 
In the Athens limestone on the northwest side of U. S. (Lee) Highway 11, 
3 mile southwest of Lacey Springs, slabs can be obtained that contain many 
specimens of this species. These specimens are sufficiently mineralized to with- 
stand etching in dilute hydrochloric acid. Many fine specimens preserving the 
details of the interior to perfection have been obtained. 
CONOTRETA PLANA Cooper, new species 
Plate 16, F, figures 24-27 
Shell large for the genus, pedicle valve hemiconical in lateral profile; outline 
almost circular except for the flattened posterior margin. Angle formed by flat- 
tened area and anterior slope about 50°; apical angle about 70°. Pseudointer- 
area broadly triangular, occupying more than half the width. Lateral slopes 
from pseudointerarea narrowly rounded. Pseudointerarea gently procline; beak 
bent a little anterior to the plane of the pseudointerarea. 
Brachial valve unknown. 
Measurements in mm.—Holotype, length 4.8, width 5.5, posterior slope 3.5, 
anterior slope 5.0, width of pseudointerarea 3.2. 
Types—Holotype: 109735b; unfigured paratype: 109735a. 
Horizon and locality—Effna formation in Virginia: Porterfield Quarry, 
5 miles east of Saltville, Maccrady (T.V.A. 218-NW) Quadrangle. 
Discussion—This species can be recognized by the broad, flat pseudointer- 
area which occupies more than half the posterior surface. It differs in this re- 
spect from all other species described herein. 
CONOTRETA RUSTI Walcott 
Plate 16, H, figure 41 
Conotreta rusti Watcott, Proc. U. S. Nat. Mus., vol. 12, p. 365 (extract 1889), figs. 1-4, 
1890.—HALL and CLarkE, Pal. New York, vol. 8, pt. 1, p. 104, pl. 4, K, figs. 16-21, 1892. 
Types.—Lectotype: 18443a (fig. 1) ; paratype: 18443b. 
Horizon and locality—Trenton limestone in New York: Trenton Falls. 
Salona formation in Pennsylvania: At Salona. 
CONOTRETA TRIANGULATA Cooper, new species 
Plate 28, A, figures 1-4 
Shell large for the genus, outline an irregular cone, nearly planoconvex; sur- 
face exfoliated. Pedicle valve with elongate-oval cross section, short posterior 
slope, and a long but steep anterior slope; lateral slopes steep; false interarea 
narrow. Brachial valve elongate oval with posterior margin somewhat more 
narrowly rounded than the anterior margin; nearly plane in profile. 
Measurements in mm.—Holotype, length 9.9, brachial length 9.2, midwidth 
8.8, thickness 5.4. 
