294 



PROCEEDINGS OF THE ACADEMY OF 



[1899. 



Fig. 4. Enamel pattern of Microtus albicauda (a), 31. cricelulus (b), and 

 M. acrophilus (c). (X 6.) 



Microtus albicauda (True). 



1894. Arvicola albicauda True, Proe. U. S. National Museum, xvii, 



p. 12. May 8, 1894. 

 1896. Microtus albicauda Miller, North American Fauna, No. 12, p. 



54. July 23, 1896. 



Type locality. — Braldu valley, Baltistan. 



Specimens collected. — Dr. Abbott took only one specimen of 

 Microtus albiccmda. 



Skull. — The skull of the type measures: greatest length, 26.4; 

 basal length, 24.4; basilar length, 23; zygomatic breadth, 15; 

 mastoid breadth, 13.4; interorbital constriction, 4.4; length of 

 7.8; anterior breadth across nasals, 3.8; posterior breadth 

 nasals, 1.8; diastema, 7.8; palatal length, 12.6; occipital 

 depth, 7.6; fronto-palatal depth (at middle of molar series), 7; 

 mandible, 16; maxillary tooth row (alveoli), 6.6; mandibular 

 tooth row (alveoli), 6.4. 



Remarks. — Microtus albicauda is apparently most closely related 

 to M. stracheyi and M. cricetulus. With both of these it agrees in 

 color and in general size. From the former it is separable by its 

 simpler m 1, from the latter by its more complex m 3, longer tail 

 and more lightly built skull. From M. blanfordi it is distinguish- 

 able at a glance by its shorter, more closely haired, entirely white 

 tail. 



Measurements. — For measurements of Microtus albicauda see 

 table, p. 298. 

 Microtus cricetulus sp. nov. 



Type adult d (skin and skull). No. 84,043, United States 

 National Museum, collected on the banks of the Tso K^iin, Ladak 

 (altitude, 16,000 feet), August 11, 1897, by Dr. W. L Abbott. 



General characters. — Similar to Microtus albicauda (True), but 

 with more heavily built skull and much shorter tail. 



