78 NEW YORK STATE MUSEUM 
and most wonderful animal of all, did not appear until the last 
(Quaternary) period of earth history. Birds developed to much 
like their present forms. Reptiles diminished both in size and 
number of species in a remarkable way, while fishes took on a 
decidedly modern aspect. The invertebrates of the Tertiary were 
not strikingly different from those of the present and by the close 
of the period they were so modern that from 75 to go per cent of 
them were even the same species as those now living. 
We learned that, in the late Mesozoic, true flowering plants had 
been developed in abundance, and during the Tertiary these and 
all other plants reached a development which in no essential way 
was different from that of the present. 
The records of Tertiary life are but scantily represented in New 
York because of the small extent of exposed Tertiary rocks. In 
the deposits of the Atlantic Coastal plain, however, abundant 
fossils are found. 
Development of relief features. The uplift of the:great Cretacic 
peneplain was an event of prime importance for New York because 
it literally furnishes us with the beginning of the history of most 
of the existing relief features of the State. Hence we assert with 
emphasis that all the principal topographic features of the State as 
we see them today date from the uplift of the Cretacic peneplain 
because they have been produced by the dissection of that upraised 
surface. This dissection was largely the work of erosion, though 
in the eastern Adirondack region faulting has produced notable 
effects. All the great valleys such as the Champlain, St Lawrence, 
Black river, Mohawk, and Hudson have been produced since the 
uplift of the peneplain. It should also be stated that the Great 
Lakes, as well as the numerous lakes, gorges, and waterfalls for 
which New York is noted, were absent as | geographic features at 
the opening of the Cenozoic. 
As previously stated, the streams of New York which flowed 
upon the peneplain surface sluggishly meandered over deep alluvial 
or flood-plain deposits, and their courses were little if any 
determined by the character of the underlying rocks because hard 
and soft rocks alike were worn down to a general level. The 
uplift of the peneplain, however, greatly revived the activity of 
the streams so that they became very effective agents of erosion; 
they first cut channels through the alluvial deposits and then into 
the underlying bedrock. Thus these large original streams had 
their courses determined in the overlying deposits, and when the 
underlying rocks were reached the same courses had to be pursued 
