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Show 1 9 0 5 .] 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 * * Hylocles rhodopis. * Anolis nebidosus. '* Zamenis mentovarius. * Rhadinea vittata. * Leptophis mexicana. * ,, diplotropis. * Leptodira albofusca. * Xenodon rhabdocephalus (?). Geophis chalybea. Trimorphodon upsilon. Elaps fulvius. 111. 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 H. 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 is not known from the plateau. Hyla eximia. * Bufo intermedins. * Hylodes palmatus. Sceloporus variabilis. * Sceloporus formosus. ,, acanthinus. ,, spinosus (?). Coronella microphoUs. The list {infra, pp. 232-233) contains 70 species, of which 8 (Diploglossus, Xenosaurus, 1 Zamenis, 3 Leptophis, 1 Drymobms, 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 " Jalapa "), Scaphiopus multiplicatus, Bufo compactus, Hyla miotympanum (?), Phrynosoma orbiculare, Tropidonotus variabilis, „ scaliger, Homalocranium bocourti, Crotalus miliarius, ,, salvini, we get a total of about 42 species, equalling 17 per cent., as restricted to the cold and cool zones (cf. p. 228). |
