WILLIAM B. DWIGHT. 207 
little west of the line of the Trenton ledge previously 
found on Kimlin’s farm. The lithological character of 
the strata would indicate that much of the rock in this 
neighborhood is of the Potsdam horizon, though it is 
difficult to find in it fossils of any kind. A subsequent 
discovery made on April 28th, corroborates the evidence 
of the facts on Kimlin’s farm, while it is far more inter- 
esting and instructive. The Spackenkill creek road 
leaves the south road (on Albany post road,) at school 
house No. 2, and leads easterly; it therefore crosses 
this limestone belt. Ata point in this road a little less 
than a mile from the school house, a road crosses into it 
from the Varick farm-house. At the junction of these 
roads, and extending some distance along the Varick 
road, isa low ledge of dark, compact limestone, lying 
mostly beneath the surface of the ground, which has 
proved to be rich in Potsdam fossils. The best locality 
for these was about a hundred feet from the Spacken- 
kill road, and almost in the middle of the Varick road. 
By making an excavation here, under permission of the 
roadmaster, I obtained quite a considerable supply of 
slabs and smaller specimens, in which glabellas and free 
cheeks of trilobites, in an excellent state of preserva- 
tion, and other fossils, were crowded together. Lingu- 
lepis pinniformis, and the allied species found on the 
Smiley farm, are quite frequent here. The trilobites are 
all of two species not yet identified among the trilobites 
of the last-mentioned locality. These are respectively, 
Ptychoparia saratogensis, Walcott, and Ptychoparia 
calcifera, Walcott; previously discovered by Mr. C. D. 
Walcott in the Potsdam strata of Saratoga county ; 
they were described by him (under the names Bathy- 
urus armatus, and Conocephalites calcifera), in the 
Thirty-Second Annual Report of the New York State 
Museum of Natural History, but he has not yet pub: 
lished any figures of them. They may be readily dis- 
o1 
