Mexican Amphibians and Reptiles. 701 
*Alylodes rhodopis, up to 10000‘ 
*Anolis nebulosus, „ ,„ 8000 
*Rhadinea vittata, „ „ 7000 
*Elaps fulvius 7000.) 
Trimorphodon ypsilon, probably going below 1000, and up to 7000’ 
*Bufo intermedius, up to 7000. 
All those marked * attain this high level on mountains! Alylodes, 
in spite of its enormous amplitude of range, is common, even plentiful, 
only from 7000‘ upwards, rare in the Hotlands; Anolis is abundant 
in the tropics, but rare above 7000’; Rhadinea is also common in 
the Tropics, but rare above 6000‘, and the usual range of Bufo 
intermedius is between 3000 and 5000 feet elevation. 
Chief result: Southern or Hotland species ascending 
into the higher zones are liable to lose their specific 
characters and to assume others, l.e. they change into 
different species. Or, if this statement be dislikened: Endemic 
tropical genera are in the higher zones represented by different, 
short-ranged species, whilst the long ranged species have attained 
their long range by having been drawn onto mountains. The latter 
statement is certainly a sure way of obscuring an important issue. 
But the fact remains that Southern genera have such species which 
are now restricted to temperate, or even to cool zones, besides species 
which are still in the Hotlands although reaching far into the cool; 
whilst — as we shall see further on — Northern genera possess plenty 
of species descending right into the Hotlands, or even to sealevel, 
without losing their hold upon their native cooler zone. 
The effect upon the Southerners of ascent or extension into 
higher altitudes can be traced also in another way: out of a total 
of 44 species 34 occeur in the hot low-lands, within the first 1000 feet, 
whence their range extends upwards as shown in List A. Let us 
consider the top levels of these species. 
In the following table the second column shows the number of 
species which actually occur at the various altitudes. 
5000° 18—=41°/,, of which including 
no longer completely 
at sealeve] 9 = 50°), changed species 3 = 33°), 
6000° 15 — 34 5 I= 60 X 4 — 44 
7000' 12 = 27 hr 5 —66 > 4 — 50 
000° :7=16 m 5 — 7 u 4 = 80 
