MICROTUS. 183 



orbital constriction very considerable; rostrum narrow. First upper 

 molar with spur at base of posterior angle. 



Color. Above umber brown, mixed with black; beneath gray, 

 with a median dark cinnamon streak. Tail above black, beneath 

 gray. Feet grayish brown. 



Midsiircments. Total length, 187: tail vertebra-, 54; hind foot, 

 24; ear, 12. 



261. brewerl. [Arvicola), Baird, N. Amer. Mamm., 1857, p. 525. 



7'y/>e locality. Muskeeget Island, Massachusetts. 



Geogr. Distr. Known onlj- from type locality. 



Genl. Char. Size large; feet broad and stout; soles with six 

 tubercles; brain case longer and wider than that of M. pennsylvanicus ; 

 interparietal longer antero-posteriorly, shorter transversely. Inter- 

 parietal as wide as long. 



Color. Above grayish yellow brown ; under parts yellowish 

 white. Feet white. Tail above yellowish brown, beneath yellowish 

 white. 



Afcasurcments. Total length, 162-182; tail vertebrae, 44-54; hind 

 foot, 22. 3-24. 



263. nesophilus. {Microtus), Bailey, Science, N. S. 1898, m, 

 p. 782. 



insularis, Bailey, Proc. Biol. Soc. Wash., 1898, p. 85 {nee Lemmus 

 insularis N^ills). 



Type locality. Great Gull Island, N. Y. 



Geogr. Distr. Known only from type locality. 



Genl. Char. "Size of M. pennsylvanicus, colors darker; skull 

 shorter and wider, with spreading zygoma and deep prezygomatic 

 notches." Interparietal wider than long. 



Color. Above dark yellowish bister, below cinnamon. 



Measurements. Skull: basal length, 26; zygomatic breadth, 16.2; 

 mastoid, 12.3; length of molar series, 6.8 (Skin). Tail, 29; hind 

 foot, 20. 



263. montanus. (Arvicola), Peale, Mamm. U. S. Expl. Exped., 

 1848, p. 46. 



longiroslris, Baird, N. Am. Mamm., 1857, p. 530. 



Type locality. Head waters of Sacramento River near Mount 

 Shasta, California. 



Geogr. Distr. Northern Utah, Nevada, northeastern California 

 and eastern Oregon. 



Genl. Char. Size moderate; ear long as forefoot; tail long, two- 

 fifths the head and body. Last upper molar has three external 

 salient angles; first lower molar has five interior and four exterior. 



