LETTER OF TRANSMITTAL. 
Museum oF Comparative Zoo.oey, 
Cambridge, Mass., October 6, 1876. 
Sir: I herewith transmit for publication my report on the North American 
Hystricide. his family is represented in that portion of North America 
north of Mexico by the single genus Lrethizon. 
For the use of the material on which this report is based, I am about 
equally indebted to the kindness of the officers of the Museum of Comparative 
Zodlogy and of the National Museum. 
I am, sir, very respectfully, yours, 
J. A. ALLEN. 
Dr. F. V. Haypen, 
United States Geologist, etc., etc., Washington, D. C. 
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