LETTER OF TRANSMITTAL. 
Orrice or U. 8. GronocicaL AND 
GEOGRAPHICAL SURVEY OF THE TERRITORIES, 
Washington, D. C., November 1, 1875. 
Sir: I transmit herewith a monograph of the family Zapodide for pub- 
lication as one of the series of articles on the Rodentia of North America, 
now in course of preparation by Mr. J. A. Allen and myself. 
The present article, like others of the series, is based upon the material 
contained in the National Museum, Smithsonian Institution, including speci- 
mens collected by yourself or under your direction. It is républished, with 
much modification, from the Bulletin of the Survey, second series, No. 5, 
pp. 253-262. 
Iam, Sir, &c., 
ELLIOTT COUES, 
Asst. Surg. U. S. A., Secretary of the Survey. 
Prof. F. V. Haypen, 
United States Geologist-in-charge. 
