Fauna of the Morrow Group 
165 
mation: near Choteau (Stations 298, 302, and 307), Hulbert 
(Station 299), and Ft. Gibson (Station 303), Oklahoma. 
Productus sp. 
Plate VIII, figures 16-16b. 
A single large Productus of the P. cora type, preserved as an 
internal cast of the pedicle valve, is included in the collections 
from the Kessler limestone. Although similar to P. cora it prob- 
ably represents a distinct species. The outline is strongly trans- 
verse with the hinge-line nearly or quite as long as the greatest 
width of the valve; the ears are large and well-defined, the 
cardinal angles closely approximating 90° ; the cardinal slopes are 
very steep, the main flanks somewhat less abrupt and the venter 
even more gently convex ; the vault of the visceral cavity is dis- 
tinctly flattened above, corresponding to the transverse flattening 
of the venter; a faint mesial sinus seems to originate in the 
umbonal region and crosses the venter, becoming obsolete before 
reaching the anterior margin, although it is possible that this 
feature is due to crushing of the apparently thin shell. Strong 
concentric wrinkles cross the cardinal slopes and main flanks 
from the ears but die out upon the venter; radiating costae are 
present everywhere on the surface of the shell, with the possible 
exception of the ears, with 17 or 18 to the centimeter near the 
margins ; the bases of strong inclined spines are present on the 
ears where they have a distinctly linear arrangement and spine 
bases may be present elsewhere on the surface of the valve. 
The dimensions of the specimen in hand are: length from 
hinge-line to anterior margin, 36 mm. ; distance from umbonal 
region to anterior margin, 38.5 mm. ; length of hinge-line,+55 
mm. ; convexity of pedicle valve, about 20 mm. 
Horizon and locality. Kessler limestone : East Mountain, Fay- 
etteville, Arkansas (Station 209). 
Genus PUSTULA Thomas 
Pustula pertenuis (Meek) 
Plate IX, figures 9-9a. 
1866. Productus Cancrini. Geinitz, Garb, und Dyas in Nebr., p. 54, tab. 4, 
fig. 6. (Not P. cancrini DeKoninck.) 
Nebraska City, Nebraska. 
