42 Alexander G. Rlthven 



altitudes, but in general it may be said that the moderately wet and wet 

 forest area above 2,200 feet is without standing water except in the bromelias. 



The habitats of reptiles and amphibians may be analyzed as follows : 

 Habitats bclozu 2,200 feet: 



Terrestrial 



Ravine forest : Restricted to the lower part of the ravines ; trees 

 large, forming rather dense shade ; ground litter well developed, 

 but dryer than in the forest above 2,200 feet. 

 Scrub forest : On the ridges and in clumps on the plains ; trees 

 small, scraggly, giving little shade, interspersed with a spare growth 

 of cacti, xerophytic herbs and shrubs; ground litter very little. 

 (PI. I, fig. 2; PI. Ill, fig. I.) 



If the amphibians and riparian forms are excluded, there are few 

 differences to be observed in the fauna of these two terrestrial 

 habitats, probably because of the limited extent of the ravine for- 

 ests. On the other hand, ground and arboreal species may be 

 recognized. 



Aquatic environments: Streams (shallow and larger lower down 

 and swifter but with pools in the hills) ; ponds few in number and 

 usually with much vegetation. The fauna is without aquatic spe- 

 cies near the foothills, except possibly Kinosternon integrum, con- 

 sisting of amphibians with aquatic larval stages and such riparian 

 forms as the iguana and basilisk. 



Habitats above 2,200 feet: , 



Terrestrial 



Forest : Tropical rain forest, becoming gradually wetter from its 

 lower limits ; trees large, forming dense shade ; a deep layer of 

 forest litter. Cloud forest, in general like the rain forest, but 

 cooler and more humid, large bromelias. (PI. II; PI. Ill, fig. 2; 

 PI. IV; PI. V, fig. 2.) Fauna divisible into three groups — the 

 arboreal, bromeliadicolous, and ground forms. 



Artificial clearings 



Aquatic environments : Streams small and torrential, without 

 aquatic species of reptiles and amphibians. (PI. A', fig. r. ) 



It will be seen that seven associations of species of reptiles and amphi- 

 bians are recognized : the ground species, arlioreal species, and aquatic 

 species below 2,200 feet; and the ground species, arboreal species, brome- 

 liadicolous species, and artificial clearing species above 2,200 feet. It will 

 also be noted that these associations may be grouped into two major hab- 

 itats — the forest below 2,200 feet (in large part scrub forest and small 

 ravine forests and open cactus areas, dry litter with higher temperatures 

 and low humidity) grading through rain forest above 2,200 feet into a 

 cloud forest (dense forest, deep wet litter, large bromelias. lower, temper- 

 atures, abundant rainfall). The aquatic habitat below 2.200 feet furnished 

 no strictly aquatic forms. 



