AMERICAN BATS OF THE GENERA MYOTIS AND PIZONYX 103 



Fur and colm\ — Pelage fine and full, the longest hairs on the back 

 about 9 mm. in length. The quality and distribution of the fur are 

 essentially as in Myotis ludfugus^ but the longer hairs tend to be 

 less burnished; consequently the back is usually less glossy, a char- 

 acter not always obvious in single specimens but quite apparent when 

 series of skins of the two animals are compared. The general color 

 approximates that of two of the races of Myotis lucifugus — the 

 typical form in the east, and M. Jucifugtis ala-scensis on the northwest 

 coast. 



Skull. — The skull is narrower in proportion to its length than that 

 of Myotis litcifug'us.i so that the distance from the last molar to the 

 tip of the hamular process exceeds the distance between the last 

 molars instead of equalling it as it does in M. lucifugus, while the 

 length of the maxillary tooth row (front of canine to back of last 

 molar) very slightly exceeds the greatest palatal width including the 

 upper molars whereas in M. lucifugus the reverse is true. In dorsal 

 view the less robust rostrum is usually an evident feature of the 

 skull as compared with that of M. lucifugus, and the width of the 

 interorbital constriction less evidently exceeds that of the rostrum 

 across roots of canines (compare pi. 1, p. 7, figs. 13 and 12). From 

 the skull of Myotis evotis that of M. keemi is distinguishable by its 

 smaller size and relatively smaller auditory bullae. 



Teeth. — As compared with the teeth of Myotis lucifugus, those of 

 M. keenii may in most instances be distinguished by rather obvious 

 peculiarities in the structure of the upper molars. The protoconule 

 and metaloph are less developed, the metaloph usually confined to 

 the bottom of the valley between the bases of the hypocone and meta- 

 cone. The main cusps on the lingual side of the crown tend to be 

 less robust, a feature which is especially noticeable in the protocone; 

 this cusp, when compared with the protocone of Myotis lucifugus 

 lucifugus, having a peculiar shrunken appearance, difficult to de- 

 scribe, but appreciable after comparison of a few specimens of the 

 two animals. The cingulum, on the other hand, is better developed, 

 rather frequently extending uninterruptedly around the entire base 

 of the protocone, a condition which occurs in 13 out of 44 skulls 

 selected at random, while it is not once found in 30 skulls of M. luci- 

 fugus lucifugus. The structure of the teeth in Myotis keenii is 

 essentially similar to that in M. evotis, but the size of the molars is 

 obviously less than in the longer-eared animal, the crown of jn? 

 usually about 1.25 to 1.35 by 1.60 to 1.75 mm. instead of 1.45 to 1.50 

 by 1.95 to 2.00 mm., a difference appreciable to the unaided eye, even 

 without direct comparison of specimens. 



Remarks. — This bat may readily be distinguished from Myotis 

 lucifugus, with which it is everywhere associated, by the approxi- 

 mately equal instead of obviously graded metacarpals, nearly equal 



