574 



,,Det eneste gjennemgaaende Maerke, der skiller Vesperugo fra 

 Vespertilio og dens Slaegtninge, er vist, at p3 mangier" (the only con- 

 stant character which distinguishes Vesperugo from Vesperiilio and its 



allies, is no doubt the absence of p^). And Gerrit Miller says, speaking 

 of the genus Pipistrellus (1. c. p, 205): ,, Teeth strictly normal and not dif- 

 fering in any essential features from those of Myotis and Lasio7iycteris^ 

 except in the absence of both pm^ and pm3. . . Skull essentially as in 

 Myotis^ though with a tendency to greater breadth. External characters 

 not essentially different from those oi Myotis ..." 



But however good a generic character the premolars may have 

 proved to afford in most cases, yet there are facts, which make the fit- 

 ness of the dental formula as a generic character rather doubtful. 



2 



Already the fact that there are bats with pm — which in regard to 



3 

 all other external characters agree with bats with pm — but differ from 



o 



2 



bats with pm — is apt to show that a subdivision into genera on the sole 



ground of the dentition, at least so far as concerns the genera Myotis 

 and Pipistrellus^ is an artificial rather than a natural one. 



A still more important fact is that the premolars, especially the se- 

 cond one, are in a high degree subject to individual variation and even 

 to reduction in size and number, which may result in the non-function 

 or total absence of this tooth. Thus the essential difference between 

 the two genera is effaced, and chiefly owing to this fact, which the in- 

 stances given below tend to establish , the dentition is less available as 

 a generic character. 



As an instance of artificial classification I mention Pipistrellus 

 [Vesperugo] annectens Uohson, of which species, so far as I know, only 

 one individual has been before described. Blanford^ writes: ,,The 

 only specimen obtained is in the Indian Museum Calcutta. A skin, pro- 

 bably belonging to the same species, is amongst Mr. Hodgson's Nepal 

 collections in the British Museum". 



In the Zootomical Institute of Stockholm this interesting species 

 is represented by 3 specimens — 2 Q and 1 (J'- — in alcohol. The fe- 

 males are adult, but not the male. They are from Sumatra, and this 

 species has not before been recorded from that island. The only speci- 

 men known to Dobson has been found in Assam. They differ from 

 Dob son's description (1. c. p. 234) with respect to the measures' being 



6 W. T. Blanford, The fauna of British India. Mammalia. London 1888 

 bis 1891. p. 316. 



7 The following dimensions are taken from one of the females, and the length 

 of the tail is given approximately. 



