1905.] AMPHIBIANS AND REPTILES. 197 



Xochimilco freshwater, surrounded by meadows, wooded hills 

 with streams. 



Sierra de Ajusco, volcanic, well- wooded mountains. Contreras, 

 8090' ; Dos Rios, 8800', pines. Orizaba, 4027' ; on the east side 

 of the slope of the plateau ; valley with streams, pastures, and 

 rich vegetation, on alluvial and harddimestone terrain. Thence 

 gTadual ascent to the volcano Citlaltepetl ; dense mixed forest, 

 oak, arbutus, and pines, about 9000' ; giving way entirely to pines. 

 Tree-line about 13,500' ; then tussocks of grass. Snow -line about 

 14,500'. 



Cordoba, 2700'. Dense tropical vegetation. Thence south- 

 wards, through limestone terrain, along the foot of the slopes, 

 which are covered up to the edge with luxurious forests ; east- 

 wards bordered by savannahs. Permanent rivers with high 

 banks ; lagoons in the forests and savannahs. 



Motzorongo, Pi'esidio, and La Raya, about 1500', in foi-est land. 



Tetela, about 900', near the edge of the savannah. 



Agua fria, 100-200'; lagoons, swamps, and low forest; flat 

 country, subject to inundations. The Rio Papaloapan, with its 

 many tributaries, carries an enormous volume of thick, yellow 

 water ; much of the lower basin is for months lurder water, only 

 island-like parts standing out, used as refuges, although by no 

 means sanctuaries, by the game and other creatures. 



Then follows low, undulating, rolling, cattle-grazing land, with 

 sandy subsoil. 



San Juan Evangelista, 100'. Tropical river-bed through 

 savannahs, bordered by dense lowland forest. 



Isthmus of Tehuantepec. Eastern slope, dense humid ever- 

 green forest; on the ridge, less than 1000', open country with 

 temporary stagnant lagoons ; on the western slope prevails the dry 

 Pacific type without continuous forests, but with more scattered 

 patches of mostly deciduous trees. 



Tehuantepec, 120'. Sandy, varied terrain. 



San Mateo del Mar. Sandy, lagoons connected with the sea. 

 Flat, scanty vegetation except in occasional swamps or near the 

 lagoons, some of which are fringed with dense low brushwood 

 and small trees. 



Salina Cruz. Porj)hyritic terrain ; hilly, steep coast -range, varied 

 by promontories and fresh- and salt-water lagoons. 



From Salina Cruz and Tehuantepec northwestwards to Oaxaca. 



The coast-range, averaging 2000-3000 feet, is covered with 

 pines down to 2000 feet. Tequesixtlan, 560', in a river- valley, shut 

 off by the coast-range ; varied, rather low vegetation, volcanic 

 alluvial. Thence through mountainous country, across parallel 

 ridges. Hills at first with tropical vegetation ; oak-forests from 

 3000' vipwards, then pines prevailing, but nowhere continuous 

 forests. General character of the country dry, most of the smaller 

 rivers run dry except in the rainy reason. An intricate system of 



