CH. II] 



DIAGRAMS OF DISTRIBUTION. 



119 



tint applied to the region which they most resemble, 

 Dr Heilprin prefers to shade the transitional areas. This 

 method however is too voluminous and expensive to be 

 used in illustration of the geographical range of different 

 species, genera and families. The number of maps re- 

 quired is reduced by a plan adopted by Dr Grev^ 1 in a 

 series of papers upon the distribution of the different 

 groups of Carnivora. The areas of certain species that do 

 not overlap are coloured with different tints ; where there 

 is an overlapping the boundaries are indicated by differ- 

 ently coloured lines made up of dots or strokes or crosses 

 &c, &c. The complexity of the result thus produced 

 seems however to counterbalance the economy of space. 

 There is no doubt that maps convey a more rapid and 

 accurate impression than tables ; and Mr J. A. Allen has 

 eliminated the element of expense by suggesting diagram- 

 matic maps which can be constructed of lines and dashes 

 in ordinary use by printers. The following scheme 



Nearctic 



Neotropical 



Zoologische Jahrb. AM. f. Syst. Bd. VI. 1892. 



