AMERICAN" BATS OF THE GENERA MYOTIS AND PIZONYX 113 



49.5 ; in 10 from Colorado it averages 48.3. Calcar long, ending in a 

 minute lobule, sometimes with a rudimentary keel. 



Fur and color. — The pelage is full and soft, the individual hairs 

 about 10 mm. long on middle of back. General color a light brown, 

 varying in the subspecies. Membranes and ears usually contrasted 

 brownish black. 



Skull. — The skull (pi. 1, p. 7, fig. 7) is essentially identical with 

 that of Myotis keenii except that it is slightly larger, the auditory 

 bullae are a little more inflated, and the sagittal crest is more con- 

 stantly developed (though rarely very conspicuous). Upper profile 

 curving very gradually from rostrum to summit of skull. Adults 

 show a low but evident sagittal crest, most obvious where it crosses 

 the depression just in advance of the occiput. Lambdoid ridges low 

 but evident, meeting at the occiput when fully developed. Viewed 

 from above the brain case is oval, bulging posteriorly beyond the 

 lambdoid ridges. The length of the maxillary tooth row, as in Myotis 

 keenii, equals or slightly exceeds the palatal width including the 

 molars. 



Teeth. — In general the teeth resemble those of Myotis keenii., but 

 the upper molars show a stronger tendency to reduction of the second- 

 ary cusps and ridges; their crown area is obviously greater, the 

 crown of m? usually about 1.45 to 1.50 by 1.95 to 2.00 mm. instead of 

 1.25 to 1.35 by 1.60 to 1.75 mm. The protoconule is always low and 

 sometimes practically absent; the metaloph is rudimentary, often 

 eliminated completely so as to leave a perfectly smooth valley be- 

 tween the bases of the protocone and metacone. Protocone and hypo- 

 cone more robust than in M. keenii, rarely if ever shrinking away 

 from the margin of the crown sufficiently to permit the cingulum to 

 pass uninterruptedly around the base of the protocone. The small 

 upper premolars are seldom crowded but stand either directly in the 

 tooth row or very slightly drawn in. 



Remarks. — ^Among the American members of the genus, Myotis 

 evotis is readily distinguishable by its moderate size combined with 

 its greatly enlarged ears. Usually the ears, in well-prepared skins, 

 are black in sharp contrast with the rather pale general color of the 

 fur, a feature which when present, renders them doubly conspicuous. 



While obviously related to Myotis keenii this animal shows a 

 higher degree of specialization in the more enlarged ears and audi- 

 tory bullae, and in the more pronounced tendency to reduction of the 

 secondary cusps and ridges of the first and second upper molars. 



The series of skins available for study is not very extensive, as 

 Myotis evotis appears to be nowhere a common bat. So far as it 

 goes the material indicates that the species is divisible into two 

 rather ill-defined geographical races, a darker typical form confined 



