LETTER OF TRANSMITTAL, 



[Covering Lagomyidw, Castoroididcc, and Castorida.'] 



Cambridge, Mass., November 8, 1876. 



Sir : I transmit herewith for publication my articles on the families 

 Castoroididce, Castor idee, and Lagomyidee. The first {Castoroididce) is repre- 

 sented, so far as at present known, by the single extinct species Castoroides 

 ohioensis ; the second {Castoridai) by one living species {Castor fiber) and 

 several extinct ones ; the third (Lagomyidce) by the single living species 

 Lagomys princeps. 



The materials on which these reports are based are contained mainly in 

 the National Museum at Washington. I am, however, indebted to the Museum 

 of Comparative Zoology for important additional materials, and have been 

 further greatly aided by specimens kindly loaned me by the Boston Society ot 

 Natural History. I have also been kindly permitted to examine the speci- 

 mens of the extinct species of Castorida described by Dr. Leidy, contained 

 in the Museum of the Academy of Natural Sciences of Philadelphia. The 

 forms described by Professor Cope I know as yet only from his published 

 descriptions and figures. 



I am, Sir, very respectfully, yours, 



J. A. ALLEN. 



Dr. F. V. Hayden, 



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



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