564 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
reaching to about the middle. Cruralium small and narrow, supported by a short 
septum. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
Hypotype (pedicle valve 11110Im).... 12.7 ? 12.8 4.0 4.6 
. (brachial valve 111101k)... ? [22 13.6 3.3 6.1 
= Cay “e  trEtepel) .. sae 13.8 13.2 2.9 0.7 
Types.—Figured hypotypes: 111101k,m, I11102a; measured hypotype: 
II1101-l. 
Horizon and locality.—Plattin group (Macy formation) in Missouri: At the 
Heck Place, 14 miles south-southeast of River aux Vasses, Weingarten (15’) 
Quadrangle; Pacific, Pacific (74’) Quadrangle; northwest of Ste. Genevieve on 
the road to Bloomsdale, Renault (15’) Quadrangle; 3 miles east of Auburn, 
Elsberry (15’) Quadrangle; on the old road 1 mile northwest of the Chicago 
Summer School Camp, NW4SW3 sec. 32, T. 37 N., R. 9 E., Weingarten (15’) 
Quadrangle. 
Carters limestone in Tennessee: Below the bentonite just east of Round Lick 
Creek on U. S. Highway 7oN at Rome, Smith County; below the bentonite 
0.8 mile east of Readyville on the north side of U. S. Highway 70S, Rutherford 
County. 
Discussion.—This species is characterized by its fairly large size, strong fold- 
ing, and the half costate exterior. The costation is like that of Camerella plicata 
(Schuchert and Cooper) in having 2 costae in the sulcus and 3 on the fold, but 
the costation extends to the middle whereas it is confined to the anterior third 
in C. plicata. Furthermore, the pedicle umbo of C. bella is more inflated and 
the fold of the brachial valve originates just posterior to the middle in C. bella. 
CAMERELLA BICOSTATA Cooper, new species 
Plate 106, H, figures 45-54; plate 111, A, figures 1-15 
Shell moderately large for the genus, wider than long with the greatest width 
slightly anterior to the middle. Beak forming an angle slightly greater than a 
right angle. Posterolateral margins widely divergent; anterolateral extremities 
narrowly rounded; front margin nearly straight. Surface with posterior half 
smooth, anterior half marked by 11 costae, 2 occupying the sulcus, 3 on the fold, 
and 3 or 4 on the flanks. 
Pedicle valve slightly less deep than the brachial valve, gently convex in lat- 
eral profile with the most convex part just anterior to the umbo. Sulcus originat- 
ing at about the middle, deepening abruptly but widening gradually anteriorly, 
where it occupies about half the valve width. Flanks flat to gently concave in 
profile and with gentle slopes. 
Brachial valve gently convex in lateral profile and with the most convex part 
in the umbonal region; nearly semicircular in anterior profile. Fold not greatly 
elevated above flanks which are gently convex and slope steeply to the margins. 
Umbonal region moderately convex. 
