How old are fossils?

BY SHARAT K. ROY Assistant Curator of Invertebrate Paleontology
Geology Leaflet 9
FIELD MUSEUM OF NATURAL HISTORY CHICAGO
1927
LIST OF GEOLOGICAL LEAFLETS ISSUED TO DATE
FIELD MUSEUM OF NATURAL HISTORY CHICAGO, U.S.A.
LEAFLET 9.PLATE I.
A VIEW OF THE GRAND CANYON OF THE COLORADO RIVER, ARIZONA.
ZOROASTER IN BACKGROUND. Photograph by O. C. Farrington.
Field Museum of Natural History
DEPARTMENT OF GEOLOGY Chicago, 1927
Leaflet Number 9