LINGUL^ OF THE CHEMUNG GROUP. 13 



Lingnla cajahoga (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. 



Ge^TS DlSCIJfA ( 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. ' 



