PRODUCTELLiE OF. THE CORNIFEROHS LIMESTONE. 
137 
One or two specimens of larger dimensions in the Hamilton group have a simi¬ 
lar surface-marking, but a different form. 
Geological formations and localities. In the Corniferous limestone in Schoharie 
county, and in the Hamilton group at Moscow and Pavilion, Newport. 
Procluctella shumardiana. 
PLATE XXIII. 
Productus shumardianus : Hall, Geol. Report of Iowa, Vol.i, Part ii, pa. 499, pl.iii, f.9, and pi. vii, f.l. 
Productus spinulicostus [in part] ; Hall, Tenth Report on the State Cabinet, p. 173, 1857. 
Productus concentricus : Hall, Tenth Report on the State Cabinet, p. 180.* Geological Report of Iowa, 
Vol. i, part ii, p. 517. 
Productus pyxidatus [partim vel totum] : Hall, Geological Report of Iowa, Yol. i, part ii, p. 498. 
Shell concavo-convex, subhemispherical, wider than long : hinge-line 
nearly or quite equalling and sometimes greater than the width of the 
shell below. 
Ventral valve very convex, gibbous in the middle and on the umbo, 
which is abruptly narrowed towards the beak, and the apex incurved 
over the hinge-line ; the sides abruptly depressed towards the cardinal 
extremities, which are flattened and more or less auriculate. In one 
specimen observed, the apex is minutely truncate, and there is a 
barely perceptible line at the junction of the two valves, which indi¬ 
cates an area. 
Dorsal valve concave, often corresponding essentially with the ventral 
va^ve; but sometimes nearly flat in the upper and central portions, and 
abruptly deflected towards the margin. 
The surface of the ventral valve is marked by intermittent radiating 
ridges, gradually rising from the surface and terminating below in 
elongate spines; while upon the upper part of the shell, about the 
umbo, there are scarcely perceptible elevations of the surface above 
the bases of the spines. There are sometimes one, two, or more spines 
upon the ears, but this does not appear to be a constant character : 
the entire surface is marked by close concentric undulating striae. 
* The Geological Report of Progress referred to in this and one or two other instances was communi¬ 
cated to the Governor as the law required, but it was not published, and the matter was incorporated in 
the volumes cited. 
