256 DR. KNUD ANDERSEN ON BATS. [Apr. 7, 



variations of shade, the principal stages are these three : dark 

 smoky brown (dark type), Yandyck-brown (intermediate stage), 

 Prout's brown (light type). 



The light colour type occurs in all races, but much more fre- 

 quently in the southern than in the northern races ; about 

 75 p. ct. of the fully adult specimens examined of the southern 

 races (representing many different stages of wear of the teeth) are 

 light-coloured, as against only 25 p. ct. of the northern races. 



The subjoined table (p. 257) gives a statistical view of the 

 number of dark and light coloured individuals in the large series 

 examined. It is based exclusively on fully adult individuals (distal 

 epiphyses of metacarpals ossified), and exclusively on dried skins, 

 no spirit specimens, however well preserved, having been taken 

 into account. It will be noticed that 62 p. ct. of the available 

 individuals of the southern races have the teeth from slightly 

 worn to much worn, whereas the same is the case with a some- 

 what smaller percentage (50 p. ct.) of the northei-n races ; it may, 

 perhaps, have slightly exaggerated the final results, but a glance 

 at the table will be suflicient to prove that it cannot have had 

 any essential influence on the conclusions, which may be epito- 

 mised as follows : — (1) Light-coloured individuals are much more 

 common in the southern than in the northern races : (2) of 30 

 individuals of the northern races which, though fully adult, have 

 the teeth unworn or practically unworn, 28 are dark-coloured ; 

 of 20 individuals of the southern races, of corresponding age, only 

 half the number are dark-coloured : (3) of 20 specimens of the 

 northern races with the teeth slightly or somewhat worn, 12 are 

 dark-coloured ; of 1 8 specimens of the southern races of corre- 

 sponding age, none are dark-coloured : (4) of 9 specimens of the 

 northern races with the teeth well worn or much worn, 4 are 

 dark-coloured ; of 1 5 specimens of the southern i-aces of corre- 

 sponding age, 2 only are dark-coloured. These two conclusions 

 therefore, would seem to be well founded : that there is a well- 

 m.arked average difference of colour between northern and southern 

 races ; and that the light colour type, though sometimes (par- 

 ticularly in the southern races) occurring in adult individuals 

 with unworn teeth, is especially characteristic of the somewhat 

 more advanced age. 



Immature individuals are always dark-coloured ; of the northern 

 races the large majority of adult and aged individix-Bls are dark- 

 coloured, of the southern races a minority only. From this it is 

 concluded that the northern races have also in this respect 

 remained in a slightly more primitive stage than the southern 

 forms. One of the following paragraphs will show that a closer 

 study of the development of the head-stripes in these two groups 

 of races leads to the same conclusion. 



Indication of dorsal stripe and white ear-edgings. — One speci- 

 men of J. . j/'. JVM/^a^ce9is^s (5 ad., San Vicente, Chiapas, Mexico, 

 teeth much worn, fur rather light-coloured, U.S. N. M. no. 133044) 

 has a short longitudinal stripe on the hinder part of the back. 



