THE GEOLOGICAL HISTORY OF NEW YORK STATE 47 
In the strata of Cambric age in New York, animal or plant re- 
mains are comparatively rare, while the Ordovicic rocks throughout 
fairly teem with fossils. If any single formation deserves special 
mention, it is the Trenton limestone which is exceedingly rich in 
fossils. The type locality, at Trenton Falls, is justly famous as a 
collecting place for Ordovicic fossils. Among plants, none above 
very simple seaweeds or algae are known to have existed. Among 
animals, hundreds of species have been described as occurring in 
the Ordovicic strata of New York. These species represent all the 
more important subkingdoms and classes of animals below the verte- 
brates. Especially prominent are: corals, graptolites, star—fishes, 
brachiopods, gastropods and trilobites. All the organisms men- 
tioned lived in the salt water, and if land life forms existed we 
know practically nothing about them. It must be borme in mind 
that not a single species of that time is known to live today, so 
complete have been the evolutionary changes since the Ordovicic 
age. Certain remarkable classes of animals like the graptolites and 
trilobites, which often fairly swarmed in the Ordovicic sea, have 
been wholly extinct for millions of years. 
TACONIC MOUNTAIN REVOLUTION (CLOSE OF THE 
ORDOVICIC) 
We are now ready to discuss the second well-known mountain- 
making epoch which affected New York State. We have learned 
that sedimentation along the middle eastern border and south- 
eastern parts of the State was practically uninterrupted during all 
the Cambric and Ordovicic periods, and that some thousands of 
feet of strata had accumulated. At the same time extensive sedi- 
mentation was taking place in the seas which covered all the regions 
of the present Berkshire hills, Green and White mountains, as well 
as southward, at least as far as Virginia, over the region occupied 
by the present Piedmont plateau. At or toward the close of the 
Ordovicic period a great compressive force in the earth’s crust was 
brought to bear upon the mass of sediments which reached from 
north of New England to Virgima, or possibly farther southward. 
As a result of this compression the strata were tilted, highly folded, 
and elevated far above sea level into a magnificent mountain range 
known as the Taconic mountains. In structure, the range consisted 
of a series of rock folds, both great and small, whose axes were 
parallel to the main axis of the range, that is north-northeast by 
south-southwest. Examination of figures 14 and 20 will give the 
