1905.] 



AMPHIBIANS AND REPTILES. 



229 



recorded from the hot-lands 70 or 69 per cent. ! I have left the 

 two lists as they are, for fear that a revision would not be free 

 from bias and might thus prove too much*. 



Fairly established is the fact that the Tierra Fria is inhabited 

 by about 34 per cent., one third of the total number of species, of 

 which one half, i.e. 17 per cent., are restricted to the cool and 

 cold zone. 



Equally safe is the conclusion that in the Tierra Caliente occur 

 69 or 70 per cent., about 50 of which (51 or 43) are restricted to it. 

 This shows the richness of tropical life, especially if we consider 

 the small extent of the hot-lands in Mexico in comparison with 

 the rest of the country. 



Text-fig. 30. 



I400D rCET,' 

 iZOOO 



900O 



60D0 



3000 



SEA 



LEVEU R\^^-^'?»ANr?: rJ^^^v^^.v''-s >>:?-•? ^1 



TIERRA rRIA. 

 TIERRA TEMPLADA. 

 TIERRA CALIENTE. 



Diagram of the distribution of 250 Mexican species according to Altitude. 



( 



Southern or 

 hot-country , 

 species. 



SswN 

 ^ ' ' ' ' 



Per cent. 

 Restricted to the Tierra Caliente 44 



Ascending into temperate zone 16 



I ////// Ascending into cool zone 5 



Species restricted to the temperate zone 



6 



Northern or | 

 cool-country •{ 

 species,; 



I 



Restricted to cool and cold zone 17 



Descending into temperate zone 8 



Descending into hot zone 



4 

 100 



Further, the whole fauna is practically composed of these two 

 groups, whilst the species restricted to the temperate zone form a 

 very small minority, 6 per cent., at the utmost 10 per cent, if we 

 allow for the diificulty of classifying. 



This shows that the original stocks were either cool or tropical, 



"* Probably all the numbers of species, ns pat down for the six groups, have been 

 understated, but this would not much alter the proportions. For instance, on p. 228, 

 the species given as occurring in cool to hot zones amount to about 24, but even 

 half a dozen more might be added according to the interpretation of such 

 records as "Amula" and "Omilteme," which may mean anything from 5000 to 

 8000 feet. 



