LETTER TO THE SECRETARY. V* 



can Mammalogy. Being exhaustive of the subject, it necessarily becomes the 

 permanent basis of future work on this group, and remains an enduring wit- 

 ness to the industry, ability, and scientific acquirements of the authors. 



A word of explanation of the plan of the work will not be out of 

 place. The Report consists of eleven separate and distinct memoirs, each 

 treating of a single family. The Muridce, Zapodida, llaplodontidce, Geomyidte, 

 and Saccomyidcc are by Dr. Cones; the Leporida, Lagomyidce, Hystricida, 

 Castor oididce, Castoridce, and Sciuridce are by Prof. Allen. The authors, 

 while working together in entire accord, have prepared their i - espective por- 

 tions independently of each other, and neither is to be accredited with the 

 work of the other, or to-be held responsible therefor. Prof. Allen has alone 

 treated of the fossil species of the order. The general superintendence of 

 the volume during its passage through the press has devolved upon Dr. Coues. 

 The memoirs have been accepted for publication and put to press in the 

 order in which they have been transmitted to this office. Their sequence in 

 the volume, therefore, is not according to the natural classification, which will 

 be found upon a subsequent page. 



The Bibliography of North American Mammals (Appendix B), with 

 which the work concludes, has been contributed by Prof. Theodore Gill and 

 Dr. Coues conjointly. Though regarded by the authors as incomplete, it is, 

 nevertheless, by far the most extensive and elaborate exposition of the 

 subject extant. 



The thanks of the Survey are due to the Public Printer, the foreman of 

 printing, and the proof-readers and compositors of the Government Printing 

 Office, for the pains they have taken to render the typography of the volume 

 so creditable to all concerned. In this connection, I take pleasure in men- 

 tioning particularly Mr. William Young, who may be justly regarded as one 

 of the most accomplished proof-readers of the country, and whose zealous 

 discharge of his duties and long experience in scientific publications have 

 rendered his services invaluable. 



I have the honor to be, very respectfully, your obedient servant, 



F. V. HAYDEN, 



United States Geologist. 

 Hon. Carl Schurz, 



Secretary of the Interior, Washington, D. C. 



