240 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
sec. 28, T. 3 N., R. 20 E., Latimer County ; Round Prairie, Potato Hills, Latimer 
County. 
Discussion.—This species can be recognized by its large size relative to the 
others described and by its nearly circular form. The three specimens on which 
the species is based vary in size but indicate a species in which the two valves 
were nearly equal in convexity. In its form and subequal convexity, this species 
differs from the others herein described. 
Genus CRANIOPS Hall, 1859 
CRANIOPS ATTENUATA Cooper, new species 
Plate 22, A, figure 1 
Craniops HALL, 12th Rep. New York State Cab. Nat. Hist., p. 84, 1859. 
Shell large for the genus, oval in outline, widest slightly posterior to the mid- 
dle but narrowing anteriorly ; posterior margin more broadly rounded than the 
anterior one; apex located about one-fifth the length from the posterior margin ; 
anterior slope gently convex, long and sloping gently to the anterior margin; 
posterior slope short, steep, and gently concave. Surface smooth except for 
growth plaits which are distant and number 8 or 9. These are distant in the 
median region but crowded in the posterolateral areas. 
Measurements in mm.—Holotype, length 4.9, width 3.8, height 1.1. 
Type.—Holotype: 116708. 
Horizon and locality—aIn Alabama (near the top of the massive limestone) 
Carters formation: Quarry 0.3 miles north of Gate City, Leeds (15’) Quad- 
rangle. 
Discussion—This is a large species having a length slightly in excess of 
C. trentonensis (Hall) to which it may be compared. It differs from that species 
in having an attenuated anterior margin and in the apex being located farther 
forward of the posterior margin. 
CRANIOPS MINOR (Winchell and Schuchert) 
Pholidops trentonensis minor WINCHELL and SCHUCHERT, Geol. Minnesota, vol. 3, p. 376, 
pl. 20, fig. 40, 1893. 
Horizon and locality——Decorah formation (Guttenberg member-Ctenodonta 
bed, Ion member-Phylloporina bed), and Prosser formation (Clitambonites and 
Nematopora beds) in Minnesota. 
CRANIOPS TENUIS Cooper, new species 
Plate 22, C, figures 3-5 
Shells thin, small, often both valves in contact ; longitudinally elliptical to sub- 
oval in outline with the posterior slightly wider than the anterior. Lateral and 
posterior margins broadly rounded but anterior margin slightly more narrowly 
rounded than the posterior one. Valves subequally convex, the pedicle valve 
slightly less convex than the brachial and with the beak situated slightly anterior 
to that of the brachial valve. Brachial lateral profile with a bulge produced by 
