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tells us of two specimens of Myotis nigricans from South America in 

 which the second premolar is lacking. ,,In one specimen . . . from Lagoa 

 Santa, Brazil, the second lower premolar of the left side is lacking, and 

 the corresponding upper premolar is somewhat reduced in size. In . . . 

 from Santa Marta, Colombia, the minute second premolar is lacking 

 from the right maxillary row, and the first premolar stands nearly in 

 the centre of the space between the third premolar and the canine." 

 He also observed in individuals in his collection the tendency of the 

 second premolar to be drawn inwards from the tooth-row in both jaws. 

 It may be added that in some specimens of Myotis nigricans a 

 small postcalcaneal lobe is to be seen. 



As I have pointed out above, the systematists have used the condi- 

 tion of the anterior premolars as a characteristic of many species of 

 Myotis (cfr. D ob son 1. c. p. 285). But the condition of the premolars, 

 given by systematists as characteristic of the species, is not always found 

 in individuals which on account of other features might be referred 

 to it. I will here give one more instance of this individual variation. 



In Myotis muricola, of which species I have examined 8 specimens 

 from Borneo and Java, I found in 6 individuals the second upper pre- 

 molar (pm3] situated in the tooth-row or slightly internal to it and, 

 though small in size, visible from the outside. In 2 specimens this tooth 

 is rudimentary and probably non-functional: in one hardly penetrating 

 the gums, being quite internal to the tooth-row in the upper jaw and 

 not visible from the outside, partially drawn inwards in the lower jaw ; 

 in the other specimen the same tooth is quite internal to the tooth-row 

 in both jaws and, besides, the reduction has proceeded one more step: 

 the second premolar has not cut through the gums on the left side of 

 the maxillar tooth -row. From this to its total disappearance it is only 

 one step. 



Such a condition of the lower second premolar as the last-men- 

 tioned one in Myotis muricola seems to occur very rarely. D ob son (1. c. 

 p. 292) has found it only in one species, Myotis hasseltii, and writes as 

 follows: ,, Although the second upper premolar is very small in every 

 species of Vespertilio and in some quite internal, yet in no other species 

 is the second lower premolar quite internal, placed in the angle between 

 the closely approximated first and third premolars and not sufficiently 

 large to fill that angle". 



It may here be pointed out that, according to Dob s o n, Myotismuri- 

 cola has a small variable postcalcaneal lobe. There are, however, indi- 

 viduals without such a lobe. In other external respects it does not bear 

 any resemblance to the genus Pipistrellus^ but is a typical Myotis. 



37* 



