Fauna of the Morrow Group 
157 
1888. Productus nanus. Keyes, Proc. Nat. Sci., Phil., p. 227. 
Lower Coal Measures: Des Moines, Iowa. 
The 25 or 30 specimens which have been referred to this 
species, although including forms which are very evidently con- 
specific with the single individual upon which the species was 
based, display the minor variations which one may safely ex- 
pect in any species of Productus. In general they are apt to 
be a little more strongly convex than the type from lowa—the 
measurement of 0.25 inch for its convexity is too large— and 
the ears are usually well demarked from the umbonal slopes. 
A few of the individuals display a faint but distinct mesial sinus 
which originates at a distance from the beak and in some there 
is a conspicuous ring-like inflation close to the lateral and an- 
terior margins as in P. marginicinctus, 7 or 8 costae occur 
in 5 mm. in the central portion of the venter; the ''suddenness'^ 
with which the costae increase in number is over-emphasized 
in Meek and Worthen's description. The length of the hinge- 
line may be somewhat greater than the width of the valve an- 
terior to the hinge-line and in none of the Morrow specimens 
is it less. Spine bases are about as numerous on the ears and 
umbonal slopes as on the venter. The dimensions of two speci- 
mens are: length from hinge-line to anterior margin, 8.5 mm. 
and 8.4 mm. ; distance from umbonal region to anterior margin, 
10.4 mm. and 10.7 mm.; length of hinge-line, 12.5 mm. and 
11.2 mm. ; convexity of pedicle valve, 6 mm. and 7 mm. ; depth 
of visceral cavity between pedicle and brachial valves, 3.5 mm., 
unknown in second specimen. 
Horizon and locality. Hale formation: East Mountain, Fay- 
etteville, Arkansas (Station 149). Morrow formation: near 
Ft. Gibson (Station 303), and Gore (Station 304), Oklahoma. 
Productus cora d'Orbigny 
1842. Productus cora. D’Orbigny, Voy. dans FAmer. merid., t. Ill, pt. 4, 
p. 55, pL 5, figs. 8-10. 
1847. Productus cora. De Koninck, Mon. du Gen. Prod, et Chon., p. 50, 
pi. 4, figs. 4a, b; pi. 5, figs. 2a-d. 
Carboniferous : Guernsey County, Flint Ridge, and Zanesville, 
Ohio; between New Harmony and Mt. Vernon, Indiana; Leaven- 
worth, Indiana; Windsor, Nova Scotia; Bolivia, etc., South 
America. 
