A MONOGRAPH OF THE BATS OF NOKTII AMERICA. 85 



V. gryphus bears a close resemblance to V. albescens. Tlie ])ropor- 

 tions ill the main are the same. The thumb is of the same size in the 

 two forms. The difl'ereiices which obtain between the two species in 

 the direction of the suprahibial groove and the shape of the tragus 

 are perhaps as trenchant as any. The region at which the species are 

 collected appear to strengthen the contrasts; thus, the V. (ilbescens ot 

 southern California are easily distinguished from the 1". siibulatus of 

 New England and Canada, while the Texan examples are more diffi- 

 cult to determine. It is likely that the species is primarily tropical, 

 and in its subsequent movements to the north it underwent modifica- 

 tions, one variety following the western northern and great ]>lateau, 

 and preserving most of the jjcculiarities of the tyi)e. Another variety 

 follows the eastern path and ranges over the lower countries east and 

 north of the Mississippi Kiver, In Texas the two have scarcely vse.})- 

 arated. Material is wanting to prove the diflerence which may exist 

 between the forms between eastern and western Texas. From the 

 difierence in altitude between the coastwise lands of the east and the 

 plateau lands of the west variations in Vespertilio of the kind indi- 

 cated might be expected to exist. 



I have not been successful in detecting secondary sexual characters 

 in V. {/rt/phus. Little is known of the characters of the young (/. e., 

 with milk dentition) of this species. The fur of the venter is i)aler 

 and more yellow than in the adult. While the post<;alcaral lobe is 

 almost absent, the metacarpal bones are relatively short and of a uni- 

 form length. The antibrachial membrane is less firmly bound down 

 to the distal end of the forearm than is the case in the adult. The 

 outlines of the legs are not sharply defined. 



^Jeasllremellt8. 



[U. S. N. M. li:(20, IJayti.'hl, Wis.] 



Millimeters. 



Heail and boily (from crown of bead to l»a.se of tail) 1 



Lenj^th of arm 1 



Len<;tli of forearm 54 



First digit: 



Length of first metacarpal bone 1 



Length of i)halanges 6 



Second digit: 



Length of wecond metacarpal bone 27 



Length of first phalanx l^ 



Third digit: 



Length of third metacarpal bone 39 



Length of lir.-st ]>halanx 11 



Length of Hccond phalanx 9 



Fourth digit: 



Length of fourth metacarpal bone 39 



Length of first jihalaux 8 



Length of second phalanx 7 



