DEVONIAN SECTION OF ITHACA, N. Y. 99 
In the sections examined in the Watkin’s Glen quadrangle the 
range of all these species of Pterinea. is restricted to the Cayuta 
member of the Chemung formation, as defined in this paper, except 
in a few doubtful cases where the species run higher up than the 
supposed termination of the Cayuta member into the Wellsburg. 
Eastward, in the Harford quadrangle, the species Pterinea che- 
mungensis has been discovered at a horizon below the range of the 
other species of the Chemung fauna. The fauna with which it is there 
associated is however sufficiently distinct from the typical Chemung 
fauna to leave little doubt as to a lower horizon. In one case Clarke 
has reported it at the extreme eastern edge of the Harford quadrangle 
in association with Strophedonta cayuta.' Neither of those species 
has been discovered in the Watkin’s Glen quadrangle below the base 
of the Chemung formation. Clarke also records Stropheodonta cayuta 
in the West Hill sandstone of the Canandaigua and Naples quad- 
rangles? and in the West Hill flags and shales of the Watkins and 
Elmira quadrangles. 
While a failure to discover fossils is no evidence that they are 
wanting, it may be stated that none of the surveying party with the 
present writer examining the rocks of the Watkins Glen quadrangle 
has discovered either the Pterinea or the Douvillina below the strati- 
graphic base of the Chemung, thus making both of these species a 
fairly satisfactory evidence of a Chemung horizon for the Watkins 
Glen quadrangle, though it is not possible to say that they do not 
appear at a lower level within this province. 
Leptodesma spinigerum and Leptodesma protextum are recorded 
from Chemung Narrows and both occur in the Chemung section 
there. They, however, vary so greatly in form and differ so slightly 
from the typical Leptodesma Rogersi; and there are so many species 
defined upon slight differences of form, that it will be difficult, with- 
out a more exhaustive study than has been given them to use species 
of this genus in defining the limits of the Chemung fauna. From 
the fact of the frequent abundance of species of this genus in the zones 
carrying such other species as Tvopidoleptus carinatus and Rhipi- 
domela vanuxemi, I am inclined to think that they belong to the 
tN. Y. State Mus. Bull. 82, 1905, locality number 2499, pp. 53-70. 
2N. Y. State-Mus. Bull. 63, 1904, p. 64. 
