306 REPORT OF THE AMERFCAX COMMITTEE. 
Recent. — The terra Receyii is understood to embrace every 
kind of rock that is now in process of formation, and when de- 
scribed systematically each one is referred to its origin, whether 
marine, estuarine, lacustrine, fluviatile, torrential, glacial, seolian, 
subaerial and terrestrial. Upon maps of small scale it is not prac- 
ticable to represent these classes separately. Upon maps of a large 
scale every author uses his own symbols and devices. It is often 
convenient, where the underlying rocks are concealed by either 
recent or quaternary deposits, to use the general designation of 
Plistocene for the covering mantle. Recent might be regarded 
as nearly synonomous with Historic. We have as yet no dis- 
tinctively American classification of the deposits representing the 
geological history of man. 
