TO DAVID DALE OWEN, M.D., 



UNITED STATES GEOLOGIST. 



Sir: 111 tlie 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 3our direction, and which you submitted to me 

 for examination. 



Yours, &c., 



JOSEPH LEIDY. 



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