_Hyla ebraccata_ _Hyla loquax_ _Phyllomedusa callidryas taylori_ _Smilisca phaeota cyanosticta_ _Anolis biporcatus_ _Anolis capito_ _Anolis humilis uniformis_ _Eumeces sumichrasti_ _Ameiva festiva edwardsi_ _Imantodes cenchoa leucomelas_ _Leptophis ahaetulla praestans_ _Xenodon rabdocephalus mexicanus_ _Bothrops nasutus_ _Bothrops schlegeli schlegeli_
Nevertheless, the region also provides at least a limited amount of habitat suitable for some species that are more frequently found in open forest of a drier nature; such species include:
_Hyla microcephala martini_ _Hyla staufferi_ _Hypopachus cuneus nigroreticulatus_ _Anolis sericeus sericeus_ _Eumeces schwartzei_ _Oxybelis aeneus aeneus_
Because of the absence of sufficiently open habitat or owing to the presence of competitors, some conspicuous members of sub-humid forests are not present in southern El Petén. Conspicuous absentees are the following:
_Rhinophrynus dorsalis_ _Phrynohyas spilomma_ _Triprion petasatus_ _Anolis tropidonotus_ _Ctenosaura similis_ _Ameiva undulata_ _Cnemidophorus angusticeps_ _Conophis lineatus_ _Masticophis mentovarius mentovarius_
[Illustration: FIG. 1. Edge of rainforest along airstrip at Chinajá, El Petén, Guatemala.]
[Illustration: FIG. 2. Rainforest at edge of savanna at Toocog, El Petén, Guatemala.]
[Illustration: Interior of rainforest at Chinajá. Notice size of buttresses on large tree (_Ceiba pentandra_).]
[Illustration: Interior of rainforest at Toocog. Notice less dense vegetation as compared with Pl. 8.]
[Illustration: FIG. 1. Rainforest along Río San Román, 16 kilometers north-northwest of Chinajá.]
[Illustration: FIG. 2. Rain pond in forest at Toocog. This was a breeding site for six species of frogs.]
Our two visits to Chinajá and Toocog afforded the opportunity to gather data on the ecology of the rainforests of southern El Petén and to study the relationships between the environment and members of the herpetofauna. Tropical rainforests present the optimum conditions for life, and it is in this environment that life reaches its greatest diversity. Here, too, biological inter-relationships are most complex. This complexity is illustrated by the presence of many species of some genera, all of which are found together in the same geographic region. In the rainforests of southern El Petén there are six species of _Anolis_, five of _Hyla_, four of _Bothrops_, and three of _Coniophanes_. Obviously, the diversity of ecological niches in the rainforest is sufficient to support a variety of related species. Of the examples mentioned above, fairly adequate ecological data were obtained for most of the species of _Anolis_, which will be used to show the ecological diversity and vertical stratification of sympatric species in the rainforests.