' The Amencan Voles of the Gonis Evofomyf<. 115 



The eyes are stiicall, and the ears, except in a single species, E. 

 unguva, are long enough to project above the fur. The feet are 

 small. The tail is rather short, varying from 23 to 33 percent 

 of the total length. The fur in winter is long and soft ; in sum- 

 mer in most species it is short and harsh. Jjateral glands, simi- 

 lar to those of the subgenus Arvicola, are usually present in adult 

 males. They are situated on the flanks, one on each side, and 

 average about 10 mm. in diameter. The hair covering these 

 glands is doubly dense and usually differs in. color and texture 

 from that of surrounding parts, forming more or less consi)icu- 

 ous spots. The number of young produced at a birth varies 

 from 4 to 6, but 4 is the more common number. There are 8 

 mammse, arranged as follows: inguinal, |; pectoral, |. 



The cranial characters of Erolomys are thus summed up by Mr. 

 Gerrit S. INIiller, Jr., in his recent paper on the genera of M'wro- 

 < m ft; :*" The skull of £"170 tom7/s, . . . as compared with that 

 of the other voles, is characterized by a general weakness and lack 

 of angularity. All the outlines are full and rounded, and the 

 ridges and furrows are slightly developed, even in extreme old 

 age. The interorbital region is broader and the audital bullas 

 are larger and more inflated than usual in Microtus and Phena- 

 comys. On the other hand, the zygomata are very slender and 

 scarcely widened 'in the region of contact between the jugal and 

 the z^vgoraatic process of the maxillary. The mandible also is 

 slender and weak. The bony palate terminates in a thin edged 

 shelf continuous between the alveoli of the posterior incisors. 

 . . . The structure is very different from that found in Phena- 

 comy^i and in t3'])ical Microtus.'''' 



The teelh, while truly microtinc in the arrangement of the 

 prisms, differ from those of 3Iicwtus und resemljle those of Phena- 

 coiiiys in having the molars always two-rooted in adults and the- 

 root of the lower incisor falling sbort of the dental foramen ; they 

 differ from those of Phenacomys in the approximately equal depth 

 of outer and inner reentrant angles in the lower molars. 



Habits. — Little is known of the habits of the Arctic E. rutilus, 

 but most, and probably all, of the species inhabiting the United 

 States have very similar habits. They live in cool, moist woods 

 and brush lands, and seem to delight in the deepest shade and 

 the cover of fallen leaves, tangled weeds, and half-decayed logs. 

 Their nests are built in underground burrows, under logs, or 



* North American Fauna, No. 12, p. 43, July, 1896. 



