1905. } AMPHIBIANS AND REPTILES. 231 
the great plateau are rather abrupt and in many parts are even 
higher than the plateau itself, so that to gain the latter would 
imply a descent. There are, as mentioned elsewhere, p. 240, 
regions which offer a gradual, easy entry, and they have facilitated 
the exchange of many species, but not of all, and of course not in 
other districts. 
Species found in the hot country and on high mountains ; those 
excluded from the plateau are marked * :— 
* Hylodes rhodopis. * Leptodira albofusca. 
* Anolis nebulosus. _* Xenodon rhabdocephalus (2). 
* Zamenis mentovarius. | Geophis chalybea. 
* Rhadinea vittata. | Trimorphodon upsiton. 
* Leptophis mexicana. | Llaps fulvius. 
* % diplotropis. | 
III. Lastly there are some species which are difficult to group, 
whether they have descended or ascended. For instance, most 
kinds of Hylodes live rather high up; they want permanent 
moisture, and this 1. rhodopis gets on the high mountains and 
in the hot forests of the Atlantic side; only a very few returns 
have been made from the truly temperate zone, and it isnot known 
from the plateau. 
Hyla eximia. | * Sceloporus formosus. 
* Bufo intermedius. | s acanthinus. 
* Hylodes palmatus. | ss spinosus (°@). 
Sceloporus variabilis. | Coronella niicropholis. 
The list (infra, pp. 232-233) contains 70 species, of which 8 
(Diploglossus, Xenosaurus, 1 Zamenis, 3 Leptophis, 1 Drymobius, 
and 1 Sceloporus) may be deducted as probably not ascending 
beyond 6000 feet. The remaining 62 species, out of a probable 
total of 250 for Mexico from between the Isthmus of Tehuantepec 
and the line Mizantla to Mazatlan, represent about 25 per cent. 
Of these, again, 30-32 (13 per cent.) seem to be restricted to levels 
above 7000 feet. These have been marked with an asterisk (*). 
If we add to them the following 10 species, which seem to be 
restricted to the high plateau, 6000-8000 feet :— 
Spelerpes morio (also from | Tropidonotus variabilis, 
_ “ Jalapa”), : scaliger, 
Scaphiopus multiplicatus, Homalocranium bocourti, 
Bufo compactus, | Crotalus miliarius, 
- Lyla miotympanum (2), | 5 | salvar, 
Phrynosoma orbieulare, | 
we get a total of about 42 species, equalling 17 per cent., as 
restricted to the cold and cool zones (cf. p. 228). 
