1908.] DR, KNLTD ANDERSEN ON BATS. 251 



lost m^, have in the large majority of individuals preserved the 

 notch in m" into which m^ fitted ; they have, consequently, also 

 in this respect remained in a slightly more primitive stage than 

 the southern races, in which the notch, in no less than 90 p. ct. 

 of the individuals, is either conspicuously reduced or quite 

 obliteiated. 



The disappearance of the sharp angular notch between cusps 5 

 and 7 of m^ is not effected by a reduction of the large, posteriorly 

 projecting cusp 5 (which would imply a decrease in the area 

 of ni"), but, on the contrary, by a filling out of the notch, conse- 

 quently by a slight increase in the volume of m^ ; it is as if the 

 loss of m^ has been compensated by a coi-responding, or partly 

 corresponding, addition to that part of m'^ against which the 

 missing m^ was pressed : in other words, the function of the 

 missing m^ has, in the more highly developed races of A . jamai- 

 censis, been transferred, to a certain extent, to the postero- 

 internal border of m' (text-fig. 52). 



Text-fi2-. 52. 



A. Artiheus jamaicensis jamaicensis, 9 ad. St. Andrew's I. B.M. 92.12.20.6. 

 Right m^, to show strong emargination of hnider margin of tooth. X x- 



B. Artiheus jamaicensis lituratus, $ ad. Morvetes, Parana. B.M. 3.7.1.127. 

 Right m^, to show slight emargination of hinder margin of tooth. X {■ 



Reference has been made above to the fact that of 185 skulls 

 only 6 lack m^ either on one side or on both sides of the mandible, 

 and it may be worth the while drawing attention also to the fact 

 that of these 6 aberrant individuals no less than 5 belong to the 

 race A. j. jamaicensis. The number of skulls examined of this 

 race is 75, the number ox aberrant individuals 5 (about 7 p. ct.) ; 

 the number of skulls of all other races together is 110, of which 

 only one single individual is aberrant (1 p. ct.). It is probably not 

 quite accidental that in the large series examined the loss of m^ 

 is less rare in the northern group of races, m^, in A. planar ostris, 

 works against the whole surface of the small m^ and a very 

 narrow postero-internal margin of m'~. When now, as is the 

 case in the large majority (about 80 p. ct.) of individuals of the 

 northern races of A. jamaicensis, there is no compensation at all 

 for the loss of m^ {i. e., no filling up of the notch in m" into 

 which m^ fitted), then nig has exceedingly little or nothing at all 

 to work against in the upper jaw, and it appears quite conceivable 

 that in such circumstances it shows a rather more pronounced 

 tendency to disappearance. In the southern races, on the other 



