35 



in the Amboy clays and in the Dakota rocks of the West, 

 which next succeed in time the Potomac clays, the angiosperms 

 are predofninant and exhibit a variety and a 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. Hear 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 Miijsouri 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 only indicates a 

 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 Cretaceous age. The botanical 

 character of the flora of the Amboy clays will be seen from the 

 following brief synopsis : 



Algcs. A small and delicate form allied to Chondrites. 



Eqiiiseta 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, Gleichcnia dindAspidinm. 



Lycopods. None vet discovered. 



Cycads. Two species probably identical with the forms from 

 Greenland described by Heer under the names of Podozamites 

 niarginatus and P. tenuinervis. 



Conifers. Fourteen species belonging to the genera Mori- 

 conia. Brae hyphy Hum, Cimni7ighamites, Pinus, Sequoia, and 



