581 



from the outside, standing in an interspace between the second premolar 

 and the canine. In the other 10 examples the first upper premolar is 

 very small, situated inside the tooth-row, the second premolar and the 

 canine being closely approximated. 



In P. pipistrellus I found individuals in which the first upper pre- 

 molar is standing in the tooth-row and most likely functional, and others 

 in which it is drawn inside the tooth-row and thus not distinguishable 

 from the outside. 



The above-mentioned facts put it beyond a doubt as regards the 

 teeth 



1) that there exists among various species of the genus Myotis an 

 individual variation in respect to the second premolar, 



2) that within each of the afore-said species a gradual reduction 

 of the second upper and lower premolars is going on, 



3) that the final result of this reduction may be the rudimentary 

 condition or even the absence of the second premolar in both jaws, 



4) that in that way intermediate forms originate, having the dental 

 formula of the genus Pipistrellus and the external characters of the 

 genus Myotis. 



5) that there exist other bats [Plpistrellus annectens) in which cha- 

 racters of the genus Pipistrellus are in the same way associated with 

 characters of the genus MyoHs, though of course, I do not venture to 

 give an opinion as to the way in which this form has originated, 



6) that in the genus Pqnstrellus an individual variation of the first 

 upper premolar has been observed, 



7)^that, according to Leche^^^ f^ the genus Pipistrellus the first 

 upper premolar may be quite rudimentary or in some species even 

 lacking and that intermediate forms thus originate between the genus 



Pipistrellus and genera with the dental formula pm - — -. 



As regards the coracoid, judging from my own observations and 

 the facts given by the above-mentioned authors, it also seems established 



1) that a bifurcation of the coracoid is constant in the genus Pipi- 

 strellus except in one species, 



2) that the coracoid does not show any sign of bifurcation in the 

 genus Myotis except in one individual of the species Myotis nigricans, 



3) that in Pipistrellus annectens the coracoid agrees completely 

 with that of Myotis, showing no mark of bifurcation, which fact fur- 

 nishes an additional proof of its close alliance to the genus Myotis., 



4) that in the individual of the species Myotis nigricans which has 



14 1. c. 1875. 



