LETTER OF TRANSMITTAL. 



Office of U. S. Geological 



AND GeOOBAPHICAL SuRVEY OF THE TERRITORIES, 



Washington, D. C, December 1, 1876. 



Sir : I have the lienor to transmit herewith, for publication as one of the 

 series of Monographs of North American Rodentia, a memoir upon the fam- 

 ily Saccomyida. 



This article is based upon the material contained in the National Museum, 



Smithsonian Institution, including all the specimens collected by yourself, or 



by the naturalists of the Survey under your direction. It is reproduced, with 



additions and other modifications, from my paper entitled "A Critical Review 



of the North American Saccomyidae", pul)li8hed in the Proceedings of the 



Philadelphia Academy of Natural Sciences for 1875, pp. 272-327. 



I am, Sir, &c., 



ELLIOTT COUES, 



Assistant Surgeon U. 8, A., Secretary of the Survey. 



Prof. F. V. Hayden, 



U. 8. Oeologist-in-charge, Sfc., Sec. 



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