132 BULLETIISr 144, UNITED STATES NATIONAL MUSEUM 



that is, the fourth and fifth fingers are relatively short. When 

 folded, the third metacarpal falls short of the elbow by about 4.5 mm. 

 On the under side of the wing the fur extends thickly as far as a 

 line joining the knee and the middle of the humerus, and on the 

 upper side of the interfemoral membrane as far as a line joining the 

 extended knees. The minute terminal vertebra of the tail and about 

 one-half of the penultimate vertebra project free. 



Foot. — The foot is smaller and more delicately formed than in 

 Myofis lueifugus^ its length a little more than one-half that of the 

 tibia. In 10 specimens from Proctor, Vt., the ratio of foot to tibia 

 averages 50.6; in 10 from Center County, Pa., 49.3; in 10 from Mam- 

 moth Cave, Ky., 51.7. The calcar is long, about 16.5 mm., and 

 nearly equals the free border of the interfemoral membrane. It 

 usually has a low keel, but this is occasionally obsolete or absent. 

 The calcar ends in a minute projecting lobule. 



Fur and color. — The texture of the fur is extremely fine and fluffy ; 

 the hairs have a tendency, due perhaps to a slight crinkling, to stand 

 out from each other a little, as in Pipistrellus suhflavus. In com- 

 parison with the bronzy burnished-tipped fur of Myotis lucifugus 

 the pelage of this species is dull grayish chestnut, though on close 

 inspection the longer tips of the hairs are seen to be slightly polished. 

 Series of skins of the two animals are very different in appearance. 



The color is distinctive. On the upper surface tTie basal two- 

 thirds of the hair is fuscous-black, then comes a narrow grayish 

 band succeeded by a cinnamon-brown tip, so that there is a dis- ^ 

 tinctly tricolor effect, while the grayish band showing through the 

 cinnamon-brown tips gives a peculiar hoary appearance at a short jj 

 distance. Below, the fur is slaty basally, the hairs with grayish- * 

 white tips, washed more or less heavily with cinnamon brown, par- 

 ticularly at the flanks, instead of slightly yellowish as in M. luci- 

 fugus. The general effect is a pinkish white below and a dull 

 chestnut gray above. The membranes and ears are blackish brown. 

 One unusually bright skin from Proctor, Vt., is dark cinnamon 

 above, nearly " sayal brown " of Ridgway, slightly washed with the 

 same on the sides of the chest. 



JSkull. — The skull in general resembles that of Myotis lucifugus 

 lucifugus with which it agrees in length (usually 14.4 to 15 mm.). 

 In form it differs in certain details that become evident on close 

 comparison. The most striking of these is the smaller, narrower 

 brain case (6.6 to 7.2 mm. instead of 7.1 to 7.6 mm.), which instead 

 of being high and with a broadly flattened top is narrower, lower, 

 (4.6 to 5.1 mm. instead of 4.9 to 5.5 mm.) and more arched trans- 

 versely than in M. I. lucifugus. A slight but perfectly definite sagit- 

 tal crest is normally present in adults, whereas in M. I. lucifugus 

 the brain case is so broad-topped that the temporal muscles rarely 



