Mexican Amphibians and Reptiles. 695 
further data hitherto not available, at least unknown to me. If 
the whole material were at our command, a solution would bid fair 
to be possible upon the lines suggested and followed in this paper. 
The problem is a real one, because a country situated as Mexico is, 
has received and differentiated its fauna in reasonably traceable 
logically understandable ways, not by whim of aceidents or haphazard 
dispersal. Of greater importance is the question whether my method 
is applicable to other classes of animals and to other parts of the 
world. 
Species arranged according to the amplitude of their range 
in feet. 
(Diagram No. II.) 
The Curve is so good that it justifies the attempt of such an 
arrangement. Very few species have a range of more than 10000 feet 
and equally few are restricted within 1000 feet; neither of which 
facts is surprising. The majority have a range of 4000 feet, which 
is an excellent mean since it shows that most species have an ampli- 
tude a little larger than that by which the Mexicans popularly 
divide their. country into the three climatic zones of Tierra caliente, 
the same altitudes, and using the term tropical in its proper sense, in 
opposition to subtropical and temperate. 
Prof. CALVERT has been stimulated by my misunderstood assertion to 
compile a “Collection of mean annual temperatures for Mexico and Central 
America“ (in: Monthly Weather Review, Vol. 36, No. 4, p. 93—97, 
April 1908, Washington, DC.). This laborious and most useful list gives 
the latitude, altitude, and mean annual temperature of some 120 Mexican 
places. He himself has travelled extensively in that country and has laid 
particular stress upon the respective temperatures in his admirable account 
of the Distribution of the Dragonflies, in: Biologia Centrali-Americana, vol. 
Neuroptera, 1908. — In the paper quoted above he comes to the im- 
portant conclusion that a given mean annual temperature reaches farther 
north and to a greater elevation on the Pacific than on the Atlantie slope 
of Mexico. No doubt he is right, but mean annual temperatures are queer 
things, because the same figure may to composed of violent extremes or 
of small variations. Nevertheless Chilpancingo has a much cooler climate 
because it is windswept and bleak, than Orizaba, or even Oaxaca which, by 
the way, is on the Pacific side. In 1908, when crossing the Sierra madre, 
or coastrange, of Michoacan, I was again struck with the non-tropical, 
rather temperate looking aspect at 3000 ft. elevation, for instance at Carrizal, 
and on exposed parts even down to almost 2000 feet. 
45* 
