638 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
and the muscle area is located in front of it. The adductor field is deeply im- 
pressed. Inside the brachial valve the median septum is high and strong and 
supports a small cruralium, but a cardinal process is absent as usual for the 
genus. The brachial processes are long and curved. 
Types—Figured hypotypes: 11148 4a,d,e,g,o-r,t,u. 
Horizon and locality—Barnhart formation (or Macy) in Missouri: Along 
the old road 1 mile northwest of the Chicago Summer School Camp, NW4SW+4 
sec. 32, T. 37 N., R.g E., Weingarten (15’) Quadrangle; on the Fredericktown 
road, 5 miles southwest of Ste. Genevieve, Weingarten (15’) Quadrangle; 0.2 
mile south of Koch Valley School on U. S. Highway 67, Kimmswick (15’) 
Quadrangle. 
ROSTRICELLULA DECORAHENSIS (Fenton and Fenton) 
Rhynchotrema decorahense FENTON and Fenton, Proc. Iowa Acad. Sci. for 1922, vol. 20, 
p. 72, pl. 1, figs. 9-11, 1924. 
Types.—Univ. Chicago. 
Horizon and locality—Decorah formation in Iowa. 
ROSTRICELLULA ELLIPTICA Cooper, new species 
Plate 132, A, figures I-5 
Shells somewhat below medium size, elliptical in outline, sides narrowly 
rounded; the midwidth forming the widest part; apical angle about 100°; an- 
terior margin nearly straight. Sulcus with 4 or 5 costae, fold with 5 or 6 costae, 
and the flanks marked by about 8 costae. Costae of fold and sulcus more widely 
spaced than those of the flanks. 
Pedicle valve moderately convex in lateral profile and with the maximum 
curvature just anterior to the umbo; anterior profile fairly strongly convex; sul- 
cus originating at about the middle; umbo somewhat swollen. Sulcus moderately 
deep anteriorly, its width equal to about half the valve width. Flanks moderately 
swollen and steep. Beak short and strongly incurved. 
Brachial valve about equal to the pedicle valve in depth, moderately strongly 
convex, more so than the pedicle valve in lateral profile; anterior profile strongly 
convex and with steep sides. Fold originating near the middle, low throughout 
its extent. Flanks strongly swollen. 
Measurements in mm.— 
Brachial 
Length length Width Thickness 
GRIMer iS Ao ts the i eat Sie 5.2 4.8 6.8 3.5 
Paratype’ (0072Z07D) cect te cnt os 7.0 6.1 7.6 4.9 
re (TT72170):. RK REMIOR ? ? 10.0 ? 
- CIT7297G) a ore aa eer ai 5.6 5.0 6.7 3.2 
Types.—Holotype: 1172174; figured paratypes: 117217b-d; unfigured para- 
type: 117217e. 
Horizon and locality—New Market formation in Virginia: From a quarry 
