3 
LETTER OF TRANSMITTAL. 
Orrice oF Unitrep Srares GEoLocicAL AND 
GEOGRAPHICAL SuRVEY or 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 Geomyide, 
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 
Geomyide”, was published by you in the ‘“ Bulletin” of the Survey (2d ser. 
no. 2, pp. 83-90, May 11,1875); a preliminary ‘“ Synopsis of the Geomyidz ” 
appeared in the “ Proceedings” of the Philadelphia Academy for 1875 (pp. 
130-138); while the extended memoir itself formed “ Part II] —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, &e., 
ELLIOTT COUES, 
Assistant Surgeon U.S. A, 
Secretary of the Survey. 
Dr. F. V. Haypun, 
U.S. Geologist-in-charge, &c., &e. 
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