TO DAVID DALE OWEN, M_D., 
UNITED STATES GEOLOGIST. 
Sir: In the accompanying Memoir will be found a description of the fossil 
Mammals and Reptiles collected in the Mauvaises Terres of Nebraska, during 
the Geological Survey made under your direction, and which you submitted to me 
for examination. 
Yours, &e., 
JOSEPH LEIDY. 
