OF DENISON UNIVERSITY. 
^39 
Rliy nconella contracta, H. 
(Plate X, Fig. 9.) 
We are quite unable to distinguish any differences between a 
small species with very acute plicae and that described by Prof. Hall, 
from the Chemung. Prof. Hall himself made the same identification 
in 1867, and as the name was applied in 1843, ranks any other name 
in vogue for the same shell. The range of individual variation is as 
great as in that quoted. 'I'he species is rare in the free stone of mid- 
dle Waverly. 
In a genus as conservative as this one a greater vertical range of 
species is to be expected thin in many orher groups. 
Rhynchonella sioboimeata, H. ? 
(Plate VH, Fig. 23.) 
A ‘small species from just above conglomerate I. has nearly the 
form of the species quoted. The sandy matrix makes a careful study 
impossible. Our specimen is smaller and less broad than Hall’s types, 
but it is not easy to point out specific distinctions, the static character 
of the genus makes the continuance of a species during the interval 
between the horizon in question and that of the Warsaw possible. 
( 
Rhynchonella sa^erinna, Win. 
(Perhaps a variety of R. sappho, H ) 
Shell rather gibbous, thickness equal to more than one-third the 
width, transversely extended; ventral valve broadly oval to slightly 
pentagonal, with a pointed incurved beak; mesial sinus rather dis- 
tinct, narrower than one-third the width, extending less than half way 
to the beak, with three to four strong plicae ; lateral surfaces convex, 
with five or six plicae on either side, which father rounded above; lat- 
eral margins nearly straight, meeting the beak at an angle of about 
110°; length of lateral margins greater than half the length of the 
valves, intersecting the evenly-curved ventral margin at a point in 
