PROCEEDINQS 



OF THE 



WASHINGTON ACADEMY OF SCIENCES 



Vol. I, pp. 15-110. May, 9, 1S99. 



REVISION OF THE SQUIRRELS OF MEXICO AND 

 CENTRAL AMERICA.! 



By E. W. Nelson. 



CONTENTS. 



Introduction P- I5 



Physiography of the Region 17 



History and Nomenclature 18 



Notes on Distribution and Variation . . , 20 



Subgenera of North American Squirrels 23 



Key to Species 33 



List of Species with Type Localities 36 



Systematic Descriptions of Species 38 



INTRODUCTION. 



The arboreal squirrels inhabiting the region between the 

 southern border of the United States and the Isthmus of Pan- 

 ama have been studied by several authors, notably J. E. Gray, 

 E. R. Alston and J. A. Allen. The material at the disposal of 

 these revisers was of the most fragmentary character, often 

 without definite localities and in poor condition, hence it is 

 hardly surprising that their conclusions are unsatisfactory. 



During the past few years the quantity of material has been 

 greatly increased and its quality much improved. Mr. G. K. 

 Cherrie and Senor Anastacio Alfaro in Costa Rica; Dr. Chas. 

 W. Richmond in Nicaragua ; Mr. A. Forrer, the Lumhollz Ex- 

 pedition, and the late Dr. Audley C. Buller in Mexico, and 

 Dr. E. A. Mearns, U. S. A., on the Mexican Boundary, have 



1 Recommended for publication by the Biological Society of Washington, 

 February 25, 1899. 



Proc. Wash. Acad. Sci., May, 1899. (15) 



