LETTER OF TRANSMITTAL. 



Museum op Comparative Zoology, 



Cambridge, Mass., October 6, 1876. 

 SiK : I herewith transmit for publication my report on the Nortli American 

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

 north of Mexico by 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. HAYDEhf, 



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



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