LETTER OF TRANSMITTAL. 



Office of United States Geological and 



Geograiiiical Survey of the Territories, 



Washington, D. C, January 1, 1877. 



Sir : I transmit herewith, for publication with the series of "Monographs 

 of North American Rodentia", a summary statement of the family Gcomyida; 

 which completes my labors in this connection. 



A word of explanation is here required. I finished my investigation of 

 this family of North American Mammals, and prepared a memoir on the sub- 

 ject, before the present series of Monographs of the Rodents was projected. 

 A very brief article, entitled " The Cranial and Dental Characters of 

 Gconryidce", was published by you in the " Bulletin" of the Survey (2d ser. 

 no. 2, pp. 83-SO, May 11,1875); a preliminary " Synopsis of the Geomyidse'' 

 appeared in the "Proceedings" of the Philadelphia Academy for 1875 (pp. 

 130-138); while the extended memoir itself formed " Part III. — Zoology" 

 (pp. 215-285) of Powell's -'Exploration of the Colorado of the West", and 

 was also reissued as a separate pamphlet, with a modification of the title. 

 Under these circumstances, it becomes inadmissible, upon considerations of 

 economy in the expenditure of funds, to duplicate the memoir at the public 

 expense. Yet it is considered in the last degree undesirable and inexpedient 

 to leave the present series of Monographs incomplete. I have accordingly 

 prepared a short article, which, omitting all details of description and criti- 

 cism not necessary to the integrity of the paper, gives the gist of the subject; 

 for the rest, I must refer you to the original memoir. I should add, however, 

 that the present paper contains no little new matter, derived from study of 

 specimens additional to those in hand in 1875, and serving to check the results 

 previously reached. 



I am, Sir, &c, 



ELLIOTT COUES, 



Assistant Surgeon U. S. A., 



Secretary of the Survey. 

 Dr. F. V. Hayden, 



U. S. Geologist-i u-charge, Sec, &c. 



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