LETTER OF TRANSMITTAL. 



Office of United 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 Norlh American Rodei.tia", a memoir on the 

 family Haplodontidce. 



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. 

 I am, Sir, &c, 



ELLIOTT COUES, 

 Assistant Surgeon United States Army, 

 Secretary and Naturalist of the Survey. 

 Prof. F. V. Hayden, 



United States Geologist-in-charge. 



35 M 



