LETTER OF TRANSMITTAL. 
OrricE of Unirep States GEOLOGICAL AND 
GEOGRAPHICAL SuRVEY OF THE TERRITORIES, 
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 on the 
family Haplodontide. 
To the single species which constitutes this family, unusual interest 
attaches, in the facts that its structure has remained very imperfectly known 
up to the present time, and that its systematic position consequently has been 
a matter of dispute. The anatomy of the species is herewith presented at 
considerable length, from original dissections; and a notice of its history and 
habits follows the description of its structure. 
Like my other memoirs of this series, the present is based upon the 
material contained in the National Museum, for the opportunity of examining 
which I am indebted to the liberal policy of the Smithsonian Institution. 
Mam, Sir, &e., 
ELLIOTT COUES, 
Assistant Surgeon United States Army, 
Secretary and Naturalist of the Survey. 
Prof. F. V. Haypey, 
United States Geologist-in-charge. 
bo) 5S 
35 M 
