40 



NORTH AMERICAN BATS. 



has given to this animal the popular appellation of the Silvery- 

 haired Bat. The posterior part of the interfemoral membrane 

 is thinly covered with short dark colored hairs : the anterior 

 surface has upon it numerous minute tufts arranged linearly. 

 Thumb small, slightly furred ; foot moderate and furred on pos- 

 terior surface. 



Fig. 36. 



S. noctivatrans. 



Skull flat, not crested ; two shallow depressions anteriorly. 



Dentition, 



Molars — 

 6 



Canines 



Incisors — 

 6 



Canines 



Molars 



=36 teeth. 



Upper Jaw. — Incisors two on either side of the median space, 

 closely approximate to but not touching canines ; nearly of the 

 same length ; centrals bifid, the teeth somewhat twisted on their 

 axis so that the two cusps have something of an antero- 

 posterior arrangement ; the internal cusp is slightly longer 

 than the external. The laterals are unicuspid, and have a basal 

 cusp. The canines are simple and moderate. Of the five molars 

 the first is very small, unicuspid, and crowded in between the 

 canine and second premolar — it is visible from the outside. The 

 second premolar has an external and internal cusp — the external 

 longer than any external point of the molars proper, while the 

 internal is shorter than any internal prominence. The other teeth 

 as usual. 



Lower Jaw. — Incisors not crowded, trifid. Canines moderate, 

 with an anterior basal point. Of the three premolars the first is 

 not so small as the second, which is about the size of the first 

 premolar of the upper jaw ; the third is about the height of the 

 molars proper, and is simple. The other teeth as usual. 



