AMERICAN BATS OF THE GENERA MYOTIS AND PIZONYX 77 



orbital constriction, narrower brain case, and in the constant presence 

 (in adults) of a low but perfectly formed sagittal crest. 



ExteiTiol characters. — The external characters as shown by a series 

 of 12 skins from Florida and four from Indiana do not differ ap- 

 preciably from those of Myotis lucifugus hicifugus otherwise than in 

 the short, dense, woolly quality of the fur, and the dull coloration 

 of the dorsal surface. Hairs at middle of back, in fresh pelage, 

 usually about 6 to 7 mm. in length instead of 9 to 10 mm. In some 

 individuals there appears to be tendency for the wing membrane to 

 be inserted at or near the ankle, but this may be due to a peculiarity 

 in the make-up of the skins. 



Fur amd color. — The fur of this species is distinctive by reason of 

 its thick, woolly appearance, resulting from the fine and rather uni- 

 form texture without a conspicuous over fur. This quality of the 

 fur, together with the lack of long burnished tips to the hairs of the 

 back as well as the absence of strong contrast in color between the 

 tips and the bases of the hairs, serves to distinguish the animal readily 

 from M. lucifugus which it otherwise somewhat resembles. The 

 actual elements of the color are essentially the same as in Myotis luci- 

 fugus lucifugus, but the shortness and inconspicuousness of the bur- 

 nished hair tips on the upperparts give a noticeable dull and luster- 

 less effect usually ranging in tint from sudan brown to Saccardo's 

 umber (Ridgway, 1912). On parting the hairs the plumbeous basal 

 area of the fur is seen to be less extensive and less dark than in M. 

 lucifugus. In some individuals the back has a peculiar drabby cast 

 which we have never seen in M. lucifugus. Underparts dull buff, 

 much as in M. I. lucifugus but the palest individual paler than usual 

 in the related animal. 



Skull. — The skull is more slender throughout than that of Myotis 

 lucifugus. While this character is most obvious in the interorbital 

 region (interorbital breadth in 16 skulls varying from 3.6 to 4.0 as 

 against 4.0 to 4.4 in 60 skulls of true M. lucifugus) it can also be 

 appreciated on direct comparison of the breadth of the rostrum over 

 bases of canines, as well as of the lacrymal breadth and the breadth of 

 brain case. A low but perfectly definite and sharp-edged sagittal 

 crest is present in all of the adult specimens examined, this character 

 alone being sufficient to distinguish the series from any similar series 

 of Myotis lucifugus. The crest resembles that present in the other- 

 wise very different species, M. velifer and M. grisesceriM?. When the 

 brain case is viewed from behind, side by side with specimens of M. 

 lucifugus from the eastern United States, the narrower, relatively 

 higher form in Myotis au^troripaHus is at once evident. In this 

 view the summit of the arch in M. lucifugus is nearly always obvi- 



