EVOTOMYS 



401 



Characters : — With a few exceptions, they resemble typical 

 MicrotincB, but are lighter, more elegantly built, and have the 

 dorsal surface usually of some shade of rufous ; deeper and 

 richer in humid, wooded regions, lighter and yellower with a 

 tendency to winter whitening in the north. The eyes and 

 more or less circular ears tend to be more conspicuous than 

 in Microtus ; the feet are small, with normal pads ; the tail 

 is shorter than in murines, longer than in Microtus ; the fur 

 is long and soft in winter, shorter and harsher in summer. 

 The mammae are 8, viz., 4 inguinal and 4 pectoral. 



The skull shows 

 some murine charac- 

 ters, being compara- 

 tively weak, and 

 lacking in angularity. 

 The outlines are full 

 and rounded, the 

 ridges, even in old 

 age, slightly devel- 

 oped. The inter- 

 orbital region is 

 broad, the auditory 

 bullae large and com- 

 paratively inflated. 

 The zygomata are usually slender, and scarcely widened 

 in the regions where the jugals and zygomatic processes of 

 the maxillaries meet ; the mandible is slender and weak. 

 The bony palate lacks the sloping part of the posterior 

 median ridge, and shows little trace of the lateral pits, 

 both so characteristic of Microtus ; it thus terminates in a 

 thin-edged shelf continuous between the alveoli of the posterior 

 cheek-teeth. This arrangement was at first thought to be 

 highly characteristic, but has since been found in other genera, 

 as Anteliomys and Eothenomys. 



The incisors are weak and slender, and those of the 

 mandible run back, each along the lingual sides of its first and 

 second cheek-teeth, crossing the tooth-row behind the latter, 

 and terminating in the ascending ramus of the mandible 

 distinctly below the dental foramen ; not rising above the level 



Fig. 60.— Palate of (a) Evotomys; (b) Microtus 

 (diagrammatic and magnified). 



