LETTER OF TRANSMITTAL. 
Orrice or U. 8. GEoLogicaL 
AND GEOGRAPHICAL SuRVEY OF THE 'l'ERRITORIES, 
Washington, D. C., December 1, 1876. 
Sir: I have the honor to transmit herewith, for publication as one of the 
series of Monographs of North American Rodentia, a memoir upon the fam- 
ily Saccomyide. 
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 Saccomyide”, published in the Proceedings of the 
Philadelphia Academy of Natural Sciences for 1875, pp. 272-327. 
I an, Sir, &c., : 
ELLIOTT COUES, 
Assistant Surgeon U.S. A., Secretary of the Survey. 
Prof. F. V. Haypen, 
U.S. Geologist-in-charge, &c., &c. whe 
