LETTER OF TRANSMITTAL. 



Museum of Cohparatite Zoology, 



Cambridge, Mass., March 15, 1K77. 



Sir: I transmit herewith for publication my memoir on the North Ameri- 

 can Sciurida, As only two genera of the Sciurida of the New World are 

 represented south of the southern boundary of the United States, and one of 

 these by only a single species not found north of that sine, I have thought it 

 best to include all of the New World forms in t}ie present memoir, thereby 

 making it a "Monograph of the American Sciuridee". The extralimital species 

 belong, with a single exception, to the genus Sciurus, which has its centre of 

 development in Mexico and Central America. It hac, however, represent- 

 atives throughout the greater part of both Americas. 



As ill the case of previous monographs of this series which I have 

 had the pleasure of transmitting to you for publication, the present memoir 

 is based mainly on the material contained in the National Museum at Wash- 

 ington, including all tliat has been collected either by yourself personally or 

 under your immediate direction and auspices. In addition to this, I have 

 been able to use a large amount of material contained in the Museum of 

 Comparative Zoology at Cambridge, Mass., without access to which my me- 

 moir would have been ikr more incomplete than it is at present In this con- 

 nection, I beg leave to express my gratitude to the officers of both these 

 institutions for their kindness in allowing me the freest access to these nlag- 

 nificcnt collections, embracing upward of two thousand specimens of the 

 American Sciurida. 



I am, Sir, very respectfully, yours, 



J. A. ALLEN. 



Dr. F. V. Hayden, 



United States Geologist, etc., etc, Washington, D. C. 





