LINGULJ3 OF THE CHEMUNG GROUP. 
15 
Lingula cuyahoga (n. s.). 
PLATE i. 
Shell subelliptical; length and breadth about as five to three ; sides 
nearly parallel, narrowing a little towards the cardinal margins ; beak 
obtuse ; cardinal slopes very little inclined; base abruptly rounded. 
Surface marked by fine concentric striae, and, on the exfoliated surface, 
by fine obscure radiating striae. 
A single valve (ventral ?) is very convex along the middle for two-thirds 
of the length ; the front rather depressed, and the entire margin, from 
the cardinal extremities, flattened. This specimen is in sandstone. 
Another imperfect specimen in soft shale has nearly the same pro¬ 
portions, but is flattened, and the cardinal slopes less nearly rectangular 
to the axis. 
The species is a well-marked and very distinct form, occurring in the thin arena¬ 
ceous layers at Cuyahoga Falls, and in the green shale at Akron, Ohio, in strata 
referred to the upper part of the Chemung group of. New-York, or Waverly sand¬ 
stone group of Ohio. 
GEKUS Discim ( Lamarck). 
This genus, though occurring in the Lower Helderberg group and in the 
Oriskany sandstone, is at present known to me in a single species only, 
in the Schoharie grit and in the Upper Helderberg limestones. It is known 
in two species in the Marcellus shale : one species is very abundant in 
the Hamilton group, and another in the Genesee slate; while the other 
known species are not of frequent occurrence. 
