1	Skull with 32 teeth	Eptesicus fuscus
1'	Skull with more than 32 teeth	2
2	Skull with 36 teeth (12 upper, 12 lower) Pelage black-brownish, with a frosting of white on back and usually on underside	Lasionycteris noctivagans
2'	Skull with 38 teeth (12 upper, 18 lower) Brownish pelage without white frosting	3
3	Skull usually less than 14.2mm long Calcar with a well developed keel	4
3'	Skull usually more than 14.2mm long Calcar without a well developed keel	5
4	Rostrum short Braincase rising abruptly, sloping Underwing furred outward to a line from the elbow to knee Color usually dark, but variable Ears short, barely reaching the nose when laid forward	Myotis volans
4'	Rostrum long and tapered Braincase rising abruptly from rostral level, flat-topped Underwing not furred Generally rich reddish-brown above and buffy brown below Dark ears extend about 1mm beyond nose when laid forward Thumbs and hind feet very small and delicate	Myotis californicus
5	Rostrum short and rising abruptly Saggital crest sometimes present Ear long, greater than 17mm When layed forward, ear extends about 4mm beyond tip of nose Fur dark brown without glossy sheen	Myotis keeni
5'	Rostrum moderately long and gradually sloping Usually without a saggital crest Ear short, less than 17mm When layed forward, ear only reaches nostril Fur reddish-brown with glossy sheen	Myotis lucifugus

Key to the small mammals of Alaska The University of Alaska Museum at the University of Alaska Fairbanks, Fairbanks, AK 99775-6960. Last modified 20 Dec 2001 by Dusty L. McDonald.