A New Rodent Genus from Mexico. 



279 



plumbeous at base; fore and hind feet white ; outer side of hind legs 

 dusky to ankles ; eyes surrounded by a narrow ring of black ; white of 

 upper lip reaching up on sides of nose half way to eye ; tail sharply 

 bicolor; dusky above, white below, and at tip all round. 



Cranial and dental characters. The cranial and dental characters have 

 been so fully given in the generic 

 diagnosis and are so well shown in 

 the accompanying drawings that 

 it will be unnecessary to describe 

 them further unless a second spe 

 cies is discovered. 



Measurements. Type specimen, 

 $ ad.: total length, 247 ; tail verte 

 brae, 121 ; hind foot, 29. Average 

 of 6 specimens from type locality : 

 total length, 244; tail vertebra, 121; 

 hind foot, 29. 



Geographic distribution. Speci 

 mens of this remarkable animal 

 were collected by Mr. Nelson in the 

 higher parts of the Sierra Madre in the western corner of the State of 

 Zacatecas, and about 100 miles farther south in the same range, near 

 Bolanos, Jalisco. Another series was obtained in a detached range, east 

 of the Sierra Madre, near Plateado, Zacatecas. Mr. Nelson informs me 

 that the animals were usually found about ledges or other rocky places 

 in the pine forest, at an altitude of 8,000 feet or upwards. Near Plateado 

 specimens were secured along the upper edge of the oak belt, where the 

 oaks mix with the lower edge of the pines. None were found at lower 

 altitudes. 



FlG ' '5- -skull 



""tomodon. 



