624 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
ANCISTRORHYNCHA GLOBULARIS Cooper, new species 
Plate 128, B, figures 6-9 
Shells small, rotund and circular when young, somewhat wider when adult; 
length and width about equal; beak obtuse; sides rounded; front margin trun- 
cated. Surface costate, with 18 to 24 costae, of which 4 to 6 occupy the sulcus. 
Pedicle valve evenly and fairly strongly convex in lateral profile with the great- 
est convexity at about the middle. Beak short and inconspicuous, incurved ; um- 
bonal and median regions swollen; sulcus originating at the middle, shallow, 
equal to about half the width at the front margin. Flanks rounded and with steep 
lateral slopes. 
Brachial valve not quite so deep as the pedicle valve; moderately convex in 
lateral and anterior profiles; median and umbonal regions slightly swollen ; fold 
low, often difficult to distinguish; flanks well rounded and steep lateral slopes. 
Measurements in mm.—Holotype, length 4.8, brachial length 4.1, width 5.0, 
thickness 3.2. 
Types.—Holotype: 111278a; unfigured paratypes: 111278b,c. 
Horizon and locahty.—Bromide formation (Pooleville member) just below 
the Viola in Oklahoma: 4 miles west and 2 miles south of Davis, Murray County. 
Discussion.—This species is the smallest of those yet described and differs from 
all others in its globular form, straight front, and considerable thickness. It is 
readily distinguished from A. costata, with which it occurs, by its smaller size 
and less transverse shells. 
ANCISTRORHYNCHA MISSOURIENSIS Cooper, new species 
Plate 128, D, figures 14-19 
Shell of about usual size for the genus, subtriangular in outline; length and 
‘width about equal; beak forming about a right angle; sides somewhat narrowly 
rounded; anterior margin gently rounded. Surface costate, about 22 rounded, 
fairly strongly elevated costae with narrower interspaces; 4 costae occupy the 
sulcus, and 5 occur on the fold. 
Pedicle valve equal to the brachial valve in depth, moderately convex in lateral 
profile and with the greatest convexity in the posterior half. Umbonal region 
narrowly swollen; sulcus originating about the middle, poorly defined. Flanks 
slightly convex, sloping steeply to the margins. 
Brachial valve gently convex in lateral profile and with the maximum con- 
vexity located in the posterior half; umbonal and median regions somewhat swol- 
len and anterolateral areas slightly less tumid. Fold scarcely visible, originating 
at about the middle and occupying less than half the width at the front. Flanks 
moderately convex with fairly steep slopes to the margins. 
Measurements in mm.—-Holotype, length 7.7, brachial length 6.7, width 7.5, 
thickness 5.3. 
Types.—Holotype: 111284a; unfigured paratype ; 111284b. 
Horizon and locality—Rock Levee formation in Missouri: Junction State 
