1898.] 



NATURAL SCIENCES OF PHILADELPHIA. 



371 



at base it is covered with short, loose hairs, similar in texture to 

 those of the body. Near the middle of the tail the hairs become 

 abruptly much elongated, stiffened and strongly directed backward. 

 The pencil thus formed is nearly as long as the tail 

 vertebrae. It is distinctly flattened from above. 

 The general appearance of the tail is much like 

 that of Dicrostonyx, but it is even more bushy 

 than in average specimens of any lemming. 



Skull. — In general form the skull (fig. 1) is 

 much like that of Evotomys alascensis, though it is 

 considerably larger. The rostrum is more taper- 

 ing than in E. alascensis, and the rostral protuber- 

 ances, 5 although apparently uninjured, are much 

 less conspicuous. The incisive foramen is consid- 

 erably shorter than in Evotomys alascensis or E. 



Fig. 4. Inner wosnessenskii ; audital bulhe of about the same 

 side of left man- , , . . ,, c ,i n i .• i • 



dible viewed ac t ua l size as in the former, therefore relatively m- 



slightly from be- termediate between the two. Mandible rather 



nn , upper g- more heavily built than in Evotomys alascensis. 



lower figure As- Teeth. — Upper incisors relatively smaller than 



chizomys. (x 3f). ' m Evotomys alascensis ; molars relatively slightly 



larger. Enamel pattern (fig. 2) apparently not essentially different 



from that of the Arctic red-backed mice. 6 The posterior upper molar 



is, however, remarkably long. It has four distinct salient angles on 



each side. 



Measurements. — Total length, 99 mm. ; head and body, 85 ; tail 



vertebras, 16; pencil, 14; hind foot, 17.5; ear from meatus, 11.5; 



ear in dry skin, 8.3. 



Skull : greatest length, 25.4 mm. ; basal length, 23.8 ; basilar 



length, 22; zygomatic breadth, 14.8; interorbital breadth, 4; 



mastoid breadth, 12.6; occipital depth, 7; fronto-palatal depth (at 



middle of molar series), 7; length of nasals, 3; incisive foramen, 



4.6; maxillary tooth row (alveoli), 6; mandible, 15; mandibular 



tooth row (alveoli), 6. 



I am permitted by the Secretary of the Smithsonian Institution 



to published this paper here. 



5 Seeantea, p. 364. 



6 See antea, p. 365, fig. 2, a-c. 



