35 
In the Amboy clays and in the Dakota rocks of the West, 
which next succeed in time the Potomac clays, the angiosperms 
are predominant and exhibit a variety anda botanical rank which 
are surprising. The Dakota flora which has been illustrated in 
the important memoirs of Mr. Lesquereux and the less volumin- 
ous contributions of Prof. Heer and myself, now stands repre- 
sented by about 200 nominal species, of which 30 are cryptogams 
and gymnosperms ; the remainder are angiosperms. Excluding 
fragmentary and doubtful material, we have about 140 species 
which, whatever their botanical relations may be, are certainly 
distinct from each other ; and of these more than three-fourths are 
arborescent angiosperms. 
The flora of the Amboy clays is closely related to that of the 
Dakota group—most of the genera and some of the species being 
identical—so that we may conclude they were nearly contem- 
poraneous, though the absence in New Jersey of the Fort Benton 
and Niobrara groups of the upper Missouri and the apparent syn- 
chronism of the New Jersey marls and the Pierre group indicate 
that the Dakota is a little the older. 
At least one-third of the species of the Amboy clays seem to - 
be identical with leaves found in the upper Cretaceous clays of 
Greenland and Aachen (Aix la Chapelle), which not onlyindicatesa 
chronological parallelism, but shows a remarkable and unexpected 
similarity in the vegetation of these widely separated countries in 
the middle and last half of the Cretaceousage. The botanical 
character of the flora of the Amboy clays will be seen from the 
following brief synopsis : 
Alge. A small and delicate form allied to Chondrites. 
Equiseta and Fungi. None yet discovered. 
Ferns. Twelve species generally similar and in part identical ; 
with those described by Heer from the Cretaceous beds of Green 
land and referred to the genera Dicksonia, Gleichenia and Aspidéum. : 
Lycopods. None yet discovered. 
Cycads. Two species probably identical with the forms from 
Greenland described by Heer under the names of Podosamites 
marginatus and P. tenuinervis. 
Conifers. Fourteen species belonging to the genera Mori- 
conia, Brachyphyllum, Cunninghamites, Pinus, Sequoia, and 
