Rcgiihitio}i of NotiicnckUnrc— Gilbert 
141 
Major categories for classification of formations. 
In Tontli Annual 
Report. 
In TwcntN -fourth Annual Report. 
Period. 
Pleistocene 
Neocene ) 
Eocene \ 
Cretaceous 
Jura-Trias 
Carboniferous 
Devonian 
Silurian 
Cambrian 
System. 
Quaternary 
Tertiary 
Cretaceous 
Jurassic 
Triassic 
Carboniferous 
Devonian 
Silurian 
Ordovician 
Cambrian 
Series. 
Recent 
Pleistocene 
Pliocene 
Miocene 
Oli^occne 
Eocene 
Permian 
Pennsylvanian 
Mississippian 
Saratogan 
Acadian 
Georgian 
Algonkian Algonkian 
Archean Arcbean 
As the new rules are much fuller than the old, it would be 
possible to indicate a large number of changes of the nature 
of additions, but for these it seems best to refer the reader to 
the actual text. Being fuller, the rules are of course more re- 
strictive, but their restrictions are mainly such as have seemed 
to be demanded by experience. As their points pf application 
are numerous, care has been taken to provide adequate ma- 
chinery for t\ieir administration. A permanent board, called 
the Committee on Geologic Names, has been instituted and 
charged with the scrutiny of all formation, group, and series 
names offered for publication in connection with Survey work. 
To this committee members of the Survey arc required to sub- 
mit the names of formations, etc.. occurring in manuscripts 
offered for publication, and the committee, which began its 
work more than a year ago. has also considered questions in 
terminology submitted to the Survey by other American geol- 
