at Green Lake, Jamesville; in the southern part of Man- 
lius, and in the northern part of Pompey. 
The Corniferous Group differs from the Onondaga 
Limestone, in that it has scattered throughout its mass, 
nodules of flint, or hornstone. Frequently these nodules 
are arranged in layers. So plentiful are these particles of 
flint, that not only has this group but the entire period 
been named from this circumstance. These nodules of 
hornstone are the remains of multitudes of small organ- 
isms; as, diatoms and desmids. Should you carefully ex- 
amine a small piece of hornstone under the microscope 
you would find it to be largely composed of the siliceous 
remains of plants and animals. Diatomaceous shells and 
spicules of sponges are the most common. As this horn- 
stone is mainly siliceous and much harder than the sur- 
rounding rock, it often happens that where it has been ex- 
posed to the weather, large masses will be found protruding 
from the parent rock. Since itis also slightly darker than 
the rest of the rock, such protrusions often appear in pecul- 
iar and grotesque shapes, which are distinctly visible. On 
account of the occurrence of these masses in the Cornifer- 
ous and Seneca Groups, and because the limestone itself 
has begun to deteriorate, for it no longer has the crystal- 
line character of the Onondaga Limestone, it contains for- 
eign matter, has a tendency to become shaly, aud shows 
in many ways its inferiority, therefore the two latter 
divisions have no very great economic value. Although 
it is almost valueless for practical purposes, it is, never- 
theless, interesting to us on account of the many evidences 
of former life which it contains. 
The Seneca Group closely resembles the preceding, 
both in structure and composition, and is not separated 
from it by any distinct line of division. It was made a 
new group because it contained a particular fossil, the 
Strophemena lineata, in great abundance. For a long 
29 
