PROCEEDINQS 



OF THE 



WASHINGTON ACADEMY OF SCIENCES 



Vol. Ill, pp. 273-295. July 26, 1901. 



SYNOPSIS OF THE RICE RATS (GENUS ORY- 



ZOMYS) OF THE UNITED STATES 



AND MEXICO. 



By C. Hart Merriam. 



The genus Oryzomys, comprising the native American Rice 

 Rats, is of tropical origin and attains its highest development 

 in South and Central America. In Mexico it is generally dis- 

 tributed except in the most arid parts, and is represented by a 

 considerable number of species and subspecies. In the United 

 States it is restricted to the southeast coast region, reaching 

 northward only as far as southern New Jersey. 



Nearly all the species are inhabitants of the Tropical and 

 Austral life regions, but in the mountainous parts of southern 

 Mexico and Central America, where boreal types are scarce 

 and often replaced by modified tropical types, a few forms have 

 pushed up into the Boreal zone and developed warm woolly 

 coats and other peculiarities which distinguish them as special- 

 ized local species. The boreal mountain forms here described 

 are crinitus from mountains bordering the Valley of Mexico, 

 and rhabdofs and angusiiceps from mountains in eastern 

 Chiapas and western Guatemala. 



Up to the present time 10 species have been described from 

 Mexico and Guatemala (including those from the peninsula of 

 Lower California and the Tres Marias Islands). To these are 

 here added 20 species and subspecies, bringing the total num- 



Proc. Wash. Acad. Sci., July, 1901. (273) 



