VOL. XII, pp. 105-108 APRIL 30, 1898 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



DESCRIPTIONS OF TWO NEW SUBGENERA AND 



THREE NEW SPECIES OF MICROTUS FROM 



MEXICO AND GUATEMALA. 



BY C. HART MERRIAM. 



Among the mammals collected in Mexico and Guatemala by 

 Mr. E. W. Nelson and his assistant, Mr. E. A. Goldman, are 462 

 specimens of Voles of the genus Microtus. These animals were 

 found on most of the mountains visited and series were obtained 

 at 34 localities. 



Up to the present time only three species of Microtus have been 

 described from Mexico, namely, mexicanus (Saussure), from Mt. 

 Orizaba, phseus (Merriam), from the Sierra Nevada de Colima, 

 Jalisco, and quasiater (Coues), from Jalapa, Vera Cruz. M. mex 

 icanus and phseus belong to the subgenus Microtus ; M. quasiater 

 to the subgenus Pitymys. Mr. Nelson's collection contains large 

 series of topotypes of these three species, and additional speci 

 mens from numerous new localities ; it contains also three new 

 species, one of which (fulviventer) belongs to the subgenus Mi 

 crotus proper; the others differ so widely from the previously 

 known groups and from each other that it is necessary to erect 

 two new subgenera for their reception. The two animals agree 

 in the character of the fur, which is long and soft, and in the 

 number of closed triangles 011 the first and last lower molars ; 

 they differ in the enamel pattern of the last upper molar, the 

 degree of inflation of the triangles and loops of all the teeth, 

 and in striking cranial characters. One is a long-tailed vole 

 from Mt. Zempoaltepec, Oaxaca ; the other a short-tailed animal 



25-BiOL. Soc. WASH., VOL. XII, 1898 (105) 



