296 TESPERTILlOXID.i:. 



vary from 2 to 4, divided by a wide space in the middle, and placed 

 in pairs or singly near the canine. The upper premolars vary from 

 one to three in number on each side ; when more than one occur, 

 the anterior premolars are generally very small, and sometimes 

 have a position inside the general line of the teeth, or tooth-row. 

 The lower premolars are 2 or 3 on each side. 



Members of this family are found throughout the tropical and 

 temperate regions of the world, extending even to many oceanic 

 islands. 



Whilst the majority of the genera are well defined and easily 

 recognized, the two great groups comprised in Vesper lujo and 

 Vesjjeriilio contain several intermediate forms, so that although 

 most of the species fall readily into two perfectly distinct genera, 

 the actual line of distinction is artificial and depends on the 

 presence or absence of an iipper premolar *, which is, in some 

 cases, not to be detected without the aid of a lens. The genera 

 found in India may be thus distinguished : — 



A . CroTvn of head but little raised above face-line ; 

 second or terminal phalanx of third or longest 

 finger not more than double length of first 

 phalanx. 



a. Ears distinctly united at base. 



a'. Ears enormous, outer margin of each ter- 

 minating behind angle of mouth Plecotus. 



b'. Ears moderate, outer margin carried fcn- 



ward and terminating above mouth. . . . Svnotus. 



b. Ears not united at base. 



a'. Ears very large, about double length of 



bead Otonyctkris. 



b'. Ears moderate, about same length as head 



or less. 



a". Outer margin of ear-conch terminating 



about haliSvay between tragus and 



angle of mouth ; 4 or 5 teeth be- 



liiud canine on each side of upper jaw. 



«'". Two pairs of upper incisors Vksperugo. 



b'". Only one pair of upper incisors; one 



on each side, close to canine .... Nvcticejus. 

 b". Outer margin of ear terminating nearer 

 to tragus than to angle of mouth. 

 a'". Nostrils tubular, projecting ; /) teeth 

 behind canine on each side of upper 



jaw IIaupyiocephalus. 



b'". Nostrils simple ; G teeth in upper 

 molar row. 



a. Nostrils crescentic Yespertilio. 



/3. Nostrils rounded Cerivoula. 



* In s])oc'iinens ])rpserved in spirit the mouth can be opened widely and the 

 teeth exaiiiiucd witli ;i niicrosco]ie if necessary. With bats, however, as with 

 other small niaiiiUiuls, it is well to extract and clean one or two skidls of each 

 species. 



