LOWER SILURIAN SYSTEM OF EASTERN MONTGOMERY CO. 423 
with very rare birdseyes” sharply separated from the underlying 
Calciferous.1 
Black river limestone. In the earlier works on New York geology 
the Black river limestone was either not separated from the succeed- 
ing mass or was confused with other rocks. In the final report on 
the first district (1843) Mather gives the following synonomy of 
the Black river limestone: “ Mohawk limestone, Birdseye limestone, 
base of the Trenton limestone, Bald mountain limestone, Blue lime- 
stone, Chazy limestone, Black marble of Isle la Motte, Seven foot 
tier, and perhaps the Neeleytown limestone, of the geological 
reports of New York, Metalliferous limerock, Transition chequered 
and sparry limerocks of Eaton, No. 2 of the Pennsylvania survey.’ 
In the firral report of Vanuxem the Black river limestone is clearly 
distinguished and described at its type locality, Black river in Jeffer- 
son county. The description is in part as follows: 
The cliff which forms the western margin of this river con- 
sists generally of a limestone in thick layers, the upper ones 
mausudiiy thick. . . “The mineral character is generally the 
same with the Birdseye, specially the layers below the upper surface 
one, being rather brittle and breaking with a smooth and 
ger sconuchoidal surface: ., -.. Phe upper part 1s, intermixed 
irregularly with black shale and exhibits the characters and 
position of the mass intermediate to the Birdseye and the Trenton 
limestone of the Mohawk which position it also holds. . . The 
Iatze and handsome’ chambered Columnmaria sulcata 
[Columnaria alveolata Goldfuss], the same which is found 
in the thick layers resting upon the Birdseye at Tribeshill, etc. is 
often seen in the exposed surface of this rock. 
In reference to the rock having the stratigraphic position of the 
Black river limestone in the Mohawk valley he says: 
On the Mohawk there are several quarries opened in a mass of 
limestone which rests upon the Birdseye as may be seen in three 
of them, and in two of which it is followed by the well characterized 
Trenton limestone. This mass therefore holds the same position 
as the upper division of the Black river limestone and contains some 
of the same fossils, but the mineral character is different, resembling 
more the gray limestone of the upper mass of the Trenton limestone. 
These quarries are Stanton’s on the south side of the Mohawk about 
113th annual report N. Y. state geologist, 1893, p. 422, 423. 
7Geology of New York, pt 1, p. 402. 
“Geology of New York, pt 3, p. 42. Tot | 
