518 



Life-histories of Northern Animals 



"First of the genus M/Vrofwj-:^ Lower incisors, with roots 

 extending far behind and on outer side of molar series; upper 

 incisors, not grooved; molars, rootless, with outer and inner re- 

 entrant angles approximately equal. Palate, with median 

 ridge, distinct lateral pits, complete lateral bridges (not ter- 



Fig. 148 — Meadow-mouse Microtus pennsyhanicus (Ord.)- 



From Toronto specimen, by Ernest Thompson Seton, 1888. 

 (Cut from Bailey's Am. Voles, Fauna 17, U. S. Biological Survey.) 



minating in posterior shelf in any American species). Tail, 

 as long as or longer than hind-foot, terete; claw of thumb, 

 pointed, not strap-shaped." 



"Second, of the sub-genus Microtus : ^ Plantar tubercles, 6 ; 

 lateral glands on hips in adult males ; * mammae, normally 8, 4 in- 

 guinal, and 4 pectoral;^ ears, usually overtopping fur; mi nor- 

 mally with 5 closed triangles;^ mj with 3 transverse loops and 

 no triangles; mz with 4 closed sections, and in most Eastern 



"Ibid., p. 10. ^Ibid., p. 13. 



* "In front of hips in xanthognathns and probably in chrotorrhinus." 



* "Four in the mexicanus group, a pair of inguinal and a pair of pectoral." 



* "With only four closed triangles in most of the Alaska species." 



