348 bulletin: museitm of comparative zoology. 



Skull. — The small delicate skull is notable for its weak canines, the 

 short and contracted rostrum. In the other races of this group the 

 roots of the upper canines cause a distinct bulge in the outline of 

 the snout as viewed from above, but in these small Mexican bats the 

 gently convex and tapering outline is not noticeably interrupted. In 

 contrast with the other races of mcgalotis the inner upper incisor is 

 normally provided with a distinct pointed cusp at its outer side. This 

 cusp is wanting in but one (91930, Biol. Surv. Coll.) among eighteen 

 skulls from Mexico that I have examined. Mr. G. S. jNIiller, Jr., 

 (1897, p. 53, fig. 10) recoi'ds variation in respect to this cusp in a series 

 from Guanajuato, in which both extremes of development are repre- 

 sented. The small size of the skull, and the short tapering rostrimi 

 distinguish it at a glance from macrotis. 



Measurements. — The tj-pe measures: forearm 39.4 mm. (average 

 of ten topot\-pes 41.1); digit III, metacarpal 37 (average of ten topo- 

 types 37.9); first phalanx 12 (average of ten topotypes 12.1); second 

 phalanx 16 (average of ten topotypes 16.8); tibia 18 (average of ten 

 topot^-pes 18.6). 



Skull: greatest length 15.6 mm.; basal length 12.5; palatal length 

 7; zygomatic breadth 8; interorbital constriction 3.4; mastoid 

 breadth 9; width of brain case 7.6; upper tooth-row 6; lower tooth- 

 row 6.2. 



Remarks. — This small dark form from the Mexican highlands has 

 till now been confused with pallescens of western United States. The 

 series of skins at present available, however, shows that it is quite 

 different in color, a very smoky appearing bat, nearly uniform in tint, 

 with none of the buff or brown tones of pallescens or toivnsendii, nor 

 the white belly of macrotis. In fall and winter pelage it seems to 

 resemble pallescens more closely but is darker. It is odd that the 

 accessory cusp of the inner upper incisor, usually wanting in other 

 races of megalotis, should be normally present in me.vicanus. In this 

 respect it resembles macrotis of the southeastern United States, but 

 otherwise shows no near approach to that species. It is further re- 

 markable that the adults are indistinguishable in color from the 

 immature individuals, which in other races are darker than the fully 

 grown specimens. 



I have provisionally considered all records of Corynorhinus from 

 south of Chihuahua as referring to the present race, but the possibility 

 that those recorded from Oaxaca or Vera Cruz may be still different 

 is not to be overlooked. Through the kindness of Mr. C. D. Bunker 

 of ihd University of Kansas Museum, I have before me a single speci- 



