16 
the ferruginous concretions of the Island Series of Staten Island, 
Long Island, Block Island and Martha’s Vineyard, all of which 
deposits are Cretaceous in age and approximately equivalent to 
the Dakota group of the West. 
About two thirds of floor case no. 6 and one quarter of floor 
case no. 7 is occupied by the New Jersey specimens and the 
remainder of case no. 7 by those from the islands to the east- 
ward. Floor case no. 8 contains specimens of the Dakota group 
flora, with which comparisons may be made. 
The flora of the Amboy clays, described by Professor J. S. 
Newberry,* had been known and the geologic age of the deposits 
in which the remains were found had been determined many years 
before any discoveries of importance had been made on the 
islands; although exposures of clay, sand and gravel, generally 
considered as probably identical with those of New Jersey, were 
more or less well known at a number of localities, notably in the 
vicinity of Kreischerville, Staten Island; Glen Cove, Long 
Island ; Block Island ; and in the celebrated cliffs at Gay Head, 
Martha’s Vineyard. Paleontologic evidence, however, was lack- 
ing, and conservative geologists, in the absence of such evidence, 
declined to recognize the exposures as the equivalents of the 
New Jersey clays and clay marls. 
In 1873, however, a geological map of the United States, 
prepared by C. H. Hitchcock and W. P. Blake, was issued in 
connection with the Ninth United States Census, on which the 
north shore of Long Island was indicated as Cretaceous. This 
feature was severely criticized by the eminent geologist J. D. 
Dana, in the American Journal of Science, who suggested that 
‘‘a number of improvements . . . may be made in the map in 
preparing it for another issue. Some of these are . . . to take 
away the green color, which means Cretaceous, from the whole 
of the north shore of Long Island, no facts making the region 
Cretaceous.” The discovery of fossil plant remains, however, 
and their identification, supplied the facts which determined the 
issue and subsequently ended all controversy. 
A few specimens of fossil leaves were found in drift bowlders 
* Monographs, U. S. Geol. Survey, vol. 26, 1895. 
