LOWER SILURIAN SYSTEM OF EASTERN MONTGOMERY cO. 421 
Mohawk valley (p. 417-22). The formation is said to have a thick- 
ness of “200 to 250 feet on the Mohawk” (p. 418). It is also 
stated that “the fucoidal layers are near the summit of the forma- 
tion.” Speaking more in detail of this member of the Calciferous 
the author Mr Darton says “ The fucoidal layers of Vanuxem are 
a characteristic member of the Calciferous over a wide area. They 
are well exposed in many of the quarries along the Mohawk, where 
they are worked extensively for building stone. . . The member 
consists of a fine grained, thick bedded limestone intermediate in 
character between the typical Calciferous and Birdseye deposits with 
intercalated streakings, blotchings, reticulations and sprinklings or 
mixtures of coarse sand and Calciferous materials of light color in 
greater part but weathering dark. The alternations are in thin 
layers at varying but frequent intervals, and the bedding of the fine 
grained material is usually more or less disjointed into a partial 
breccia. The coarse materials are disposed in forms suggesting 
fucoids, and this resemblance has given the name to the member. 
Fossils are usually present and constitute a limited but characteris- 
tic fauna. This member appears to have a thickness of about 15 
feet in the Mohawk valley ” (p. 420, 421). 
Birdseye limestone. The name “ birdseye”’ or “ birdseye marble ” 
was a popular designation of limestone containing cylindrical tubes 
which in cross section on the polished surface bore a fancied resem- 
blance to birdseye maple. Prof. Eaton uses the term in its popular 
sense in the following mention of the rock now known as Birdseye, 
“when it [metalliferous limerock=Trenton] is compact and con- 
tains numerous stylastrites, as on East Canada creek it may be 
wrought into a beautiful variety called birdseye marble.”’ In the 
Geological nomenclature of North America birdseye marble becomes 
a designation of the subdivision of the metalliferous limerock (Tren- 
ton) in which “the natural layers are pierced transversely with 
cylindrical petrifactions so as to give the birdseye appearance when 
polished” (p. 13). In another place he speaks of these vertical 
tubes as “ vertical encrinites ” (p. 23). 
In the First annual report on the geological survey of the third district 
(1837) by Mr Conrad, the Birdseye limestone is called “gray sparry 
limestone of the Mohawk valley.” Its thickness is given as 30 feet 
at Littlefalls and it is said to thin out and disappear to the east along 
4Geological and agricultural survey, district adjoining Erie canal, p. 32. 
