LETTER OF TRANSMITTAL. 



Museum of Comparative Zoology, 



Cambridge, Mass., October 6, 1876. 

 Sie : I herewith transmit for publication my report on the North American 

 Hystricidte. This family is represented in that portion of North America 

 north of Mexico hy the single genus Erethizon. 



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 

 Zoology and of the National Museum. 



I am, sir, very respectfully, yours, 



J. A. ALLEN. 

 Dr. F. V. Hayden, 



United States Geologist, etc., etc., Washington, D. C. 



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