360 PROCEEDINGS OF THE ACADEMY OF [1898. 



tinguish it from that of E. rutilus, or in fact from any other known 

 member of the genus. The anterior edge of the squamosal is pro- 

 duced to form a very distinct postorbital process, quite as in many 

 species of Microtus. The mandible is massively built and, like the 

 skull, shows a degree of angularity more in keeping with Microtus 

 than Evotomys. The palate, although damaged, appears to be that 

 of typical Evotomys. Mr. Bailey says of this species : " Evotomys 

 rufoeanus (Sundevall) of northern Europe is remarkable for its large 

 molars and almost microtine form of skull." He gives the follow- 

 ing measurements of a skull from Lapland : basal length, 25 mm. ; 

 nasals, 7.6; zygomatic breadth, 15 ; mastoid breadth, 12.2; alveo- 

 lar length of upper molar series 6.7. 



Teeth. — The teeth of Evotomys rufoeanus are chiefly remarkable 

 for their large size and great strength. Their development rela- 

 tively to the size of the skull is more in accord with the proportions 

 normal in Microtus than in Evotomys. Apparently the molars do 

 not develop as complete roots as in other species of Evotomys. The 

 root of the lower incisor is nearly as long as in some species of 

 Microtus, and the long back lower molar is encapsulated, though 

 not conspicuously so. The enamel pattern (fig. 2 d) differs widely 

 from that of Evotomys rutilus (fig. 2 a). Its most striking peculiar- 

 ities are the simplicity of the posterior upper molar, and the shallow 

 reentrant angles on the outer side of the posterior lower molar. 



Color. — A specimen in fresh autumnal pelage has a well defined 

 dorsal stripe of a color intermediate between the hazel aud cinna- 

 mon rufous of Ridgway. This stripe begins between the eyes and 

 extends back nearly to base of tail. Ears colored like dorsal stripe. 

 Sides an indescribable grizzle of hair brown, whitish, black, and 

 slate color. Whole under parts soiled bufiy-white, darkened by the 

 slaty bases of the hairs, which show through irregularly on the sur- 

 face. Cheeks, muzzle, and sides of head similar to sides of body, 

 but slightly darker. Tail sharply bicolor, brownish above, dirty 

 white below. Feet dirty whitish. 



General remarks. — Mr. Bailey has already called attention to the 

 fact that Evotomys rufoeanus " is the most divergent form of the 

 genus known." So divergent is the animal that it may well be 

 questioned whether it is to be regarded as a true Evotomys. Its 

 heavy and apparently imperfectly rooted teeth more closely resem- 

 ble those of many species of typical Microhcs than they do the weak, 

 perfectly rooted teeth of true Evotomys. The relationships of the 



