86 > Bailey New Species and Subspecies of Voles. 



163; tail vertebrae 37; hind foot 20.6. Skull of type : Basal length 27.4; 

 nasals 8; zygomatic breadth 16.7; mastoid breadth 12.2; alveolar length 

 of upper molar series 6.5. 



Microtus insularis sp. nov. 



Type from Great Gull Island, New York, No. f f{j|, $ im., Merriam 

 Coll. Collected Aug. 6, 1888, by B. H. Dutcher. 



General characters. Size of pennsylvanicus ; colors darker ; skull shorter 

 and wider with spreading zygoma and deep prezygomatic notches. 



Color. August pelage: Above, dark yellowish bister heavily mixed with 

 black hairs, darkest on nose and face ; belly dusky, washed with cinna 

 mon; feet blackish ; tail black above, color of belly below. 



Cranial characters. The skull differs from that of pennsylvanicus in 

 shorter, wider brain case ; wider and more abruptly spreading zygomatic 

 arches ; broader zygomatic shield ; smaller audital bulke ; palate short 

 with a median point or spur and deep lateral pits. Posterior upper molar 

 with second inner and outer angles approximately opposite and conflu 

 ent ; dentition otherwise similar to that of pennsylvanicus. 



Measurements. Type, measured from dry skin: Tail 29; hind foot 20- 

 Skull, No. 43969, from Little Gull Island: Basal length 26; zygomatic 

 breadth, 16.2; mastoid breadth 12.3; alveolar length of upper molar 

 series 6.8. 



Microtus angusticeps sp. nov. 



Type from Crescent City, California. No. HW> cT ad. , U. S. Nat. Mus. , 

 Biological Survey Coll. Collected June 16, 1889, by T. S. Palmer. Orig. 

 No. 151. 



General characters. Smaller and darker than typical mordax, with very 

 narrow, slender skull and small audital bnlUe. 



Color. Summer pelage : Upper parts dark bister, lined with black hairs, 

 darkest on face and nose ; sides paler; belly washed with creamy white ; 

 feet plumbeous-gray; tail distinctly bicolor, blackish above, soiled white 

 below. 



Cranial characters. Skull small and very narrow, distinctly ridged in 

 adults; nasals projecting in front of incisors; incisive foramina short; 

 audital bullse very small and constricted ; coronoid notch of mandible 

 narrow ; incisors slender ; molars small with narrow, sharp angles ; 

 enamel pattern as in M. mordax. 



Measurements. Type, tf ad. : Total length 170 ; tail vertebrae 56 ; hind 

 foot 22. Skull of type: Basal length 23.4; nasals 7.6; zygomatic breadth 

 13.5; mastoid breadth 10.8; alveolar length of upper molar series 6. 



Microtus nevadensis sp. nov. 



Type from Ash Meadows, Nye Co., Nevada. No. ff|f, 9 ad., U. S. 

 Nat. Mus., Biological Survey Coll. Collected March 2, 1891, by E. W. 

 Nelson. Orig. No. 577. 



