354 
PALAEONTOLOGY OP NEW-YORK. 
to the front. The plications on the sides are more or less abruptly 
curved to the margins of the shell. The shell, when preserved, is marked 
by fine close concentric striae : the specimens are usually casts. 
I have referred to this species some gibbous forms with moderately elevated 
mesial folds, in which the plications are subangular or rounded, and the entire 
shell preserves a rotund form. The original of this species is the largest one that 
has been observed, and is nearly an inch in length, with a somewhat greater breadth. 
The more common forms are about three-fourths of an inch in diameter. 
This species presents many features in common with JR. sappho of the Hamilton 
group ; and I am prepared to find, among larger collections, a gradation from 
one to the other. 
Geological formation and localities. This species has been found in the higher 
beds of the Chemung group ; in Chautauque county, New-York ; at Meadville, and 
iu some loose masses of the group on Oil creek, Pennsylvania. 
Rhynchonella (Stenocisma) sappho, var. 
PLATE LY. 
Specimens from the ferruginous sandstone of Licking county, Ohio, 
present all the characteristic features of R. ( S .) sappho of the Hamilton 
group. The specimens vary from about half an inch to three-fourths of 
an inch in length, with a somewhat greater breadth. The plications vary 
from obtusely angular to rounded, and often show a distinct groove 
towards the margin of the shell. 
This form is common and even abundant in the ferruginous sandstones known 
as the upper part of the Waverly sandstone series of Ohio, and it is introduced 
for comparison with the Hamilton and Chemung forms of New-York. 
