GEOLOGICAL HISTORY OF NEW YORK. 647 



but none such have yet been discovered, while a number of well-known 

 European Triassic species have been obtained from what are considered 

 as the highest portions of the group in Virginia and North Carolina. 



In the Cretaceous age the region about New York sunk below its 

 Triassic level, and the sea came in over a belt of country which was 

 before, and is now, dry land. The waves in their advance cut away 

 much of the shore which opposed their progress, both rock and soil, and 

 spread a sheet of sea-beach composed of gravel and sand as far as they 

 reached inland. This old beach we now know as the Raritan sands, 

 and they contain great quantities of leaves, branches, and trunks of 

 trees, which had grown on the sinking coast. On examination, they 

 prove to be entirely different from those contained in the Triassic rocks, 

 consisting mainly of the remains of angiospermous plants the highest 

 botanical group, and such as form the prevailing vegetation of the 

 present day. Among these Cretaceous plants we find the leaves of 

 oaks, magnolias, and other genera now living in our forests. These 

 prove that, in the long interval the Jurassic age which intervened 

 between the Triassic and Cretaceous, the vegetation of the world had 

 been completely revolutionized ; at least, that most of the genera and 

 species which prevailed during the Triassic age had passed away, and 

 been superseded by such as had been before unknown. 



When the water stood at a moderate depth over the sunken shore, 

 the Amboy clays settled down upon the sandy bottom. These were 

 apparently derived from the feldspar of the granites which compose the 

 neighboring highlands ; the quartz, unaffected by chemical action, and 

 less finely comminuted, remaining as sand and gravel nearer its place 

 of origin. 



As the water deepened, true marine conditions supervened along 

 the coast, and the first two of the New Jersey marl-beds were formed 

 from the remains of animals which inhabited the sea, and such as were 

 washed into it from the adjacent shore. The green-sand of these marl- 

 beds is derived chiefly from the countless number of microscopic shells 

 of the Foraminifera, which filled the waters of the Cretaceous sea 

 here, as in many other places. Its green color is due to glauconite, a 

 silicate of lime, potash, alumina, etc. White chalk is likewise com- 

 posed chiefly of the shells of Foraminifera, but these lived in deeper 

 water, and were of different kinds from those that produced the green- 

 sand. The fertilizing property of the marls is due to the potash and 

 phosphorus they contain. 



The marl-beds are also vast cemeteries, in which are stored the more 

 or less perfect remains of the larger land and water animals of Creta- 

 ceous times. Among these we find the shells of Ammonites the great 

 coiled cephalopods and a large number of other mollusks characteristic 

 of the Cretaceous fauna. There have likewise been discovered in the 

 marl-beds numerous remains of large reptiles, both herbivorous and car- 

 nivorous. Among these are Hadrosaurus and Lwlaps the represent- 



