US 
Bulletin of the Museum of Comparative Zoölogy 
AT HARVARD COLLEGE. 
Vor. XLIX. 
GEOLOGICAL SERIES, Vol. VIII, No. 3 
POST-PLEISTOCENE DRAINAGE MODIFICATIONS IN 
THE BLACK HILLS AND BIGHORN MOUNTAINS: 
By GEor@GE RoGERs MANSFIELD. 
Wirn Four PLATES. 
CAMBRIDGE, MASS., U. S. A.: 
PRINTED FOR THE MUSEUM. 
Marcu, 1906. 
