Volume 15, No. 5, pp. 205-249, pls. 7-10, 6 figs.

October 4, 1963 --------------

Amphibians and Reptiles of the Rainforests of Southern El Petén, Guatemala

BY WILLIAM E. DUELLMAN

UNIVERSITY OF KANSAS LAWRENCE 1963

UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: E. Raymond Hall, Chairman, Henry S. Fitch, Theodore H. Eaton, Jr.

Vol. 15, No. 5, pp. 205-249, pls. 7-10, 6 figs. Published October 4, 1963

UNIVERSITY OF KANSAS Lawrence, Kansas

PRINTED BY JEAN M. NEIBARGER, STATE PRINTER TOPEKA, KANSAS 1963

29-5935

Amphibians and Reptiles of the Rainforests of Southern El Petén, Guatemala

BY

WILLIAM E. DUELLMAN

CONTENTS

PAGE INTRODUCTION 207 Acknowledgments 208

DESCRIPTION OF AREA 208 Physiography 209 Climate 209 Vegetation 209

GAZETTEER 210

THE HERPETOFAUNA OF THE RAINFOREST 211 Composition of the Fauna 212 Ecology of the Herpetofauna 212 Relationships of the Fauna 217

ACCOUNTS OF SPECIES 218

HYPOTHETICAL LIST OF SPECIES 246

SUMMARY 247

LITERATURE CITED 247

INTRODUCTION

Early in 1960 an unusual opportunity arose to carry on biological field work in the midst of virgin rainforest in southern El Petén, Guatemala. At that time the Ohio Oil Company of Guatemala had an air strip and camp at Chinajá, from which place the company was constructing a road northward through the forest. In mid-February, 1960, J. Knox Jones, Jr. and I flew into El Petén to collect and study mammals, reptiles, and amphibians. While enjoying the comforts of the fine field camp at Chinajá, we worked in the surrounding forest and availed ourselves of the opportunity to be on hand when the road crews were cutting the tall trees in the forest, thereby bringing to the ground many interesting specimens of the arboreal fauna. We stayed at Chinajá until late March, with the exception of a week spent at Toocog, another camp of the Ohio Oil Company located 15 kilometers southeast of La Libertad and on the edge of the savanna. Thus, at Toocog we were able to work both in the forest and on the savanna. In the summer of 1960, John Wellman accompanied me to El Petén for two weeks in June and July. Most of our time was spent at Chinajá, but a few days were spent at Toocog and other localities in south-central El Petén.

Many areas in Guatemala have been studied intensively by L. C. Stuart, who has published on the herpetofauna of the forested area of northeastern El Petén (1958), the savannas of central El Petén (1935), and the humid mountainous region to the south of El Petén in Alta Verapaz (1948 and 1950). The area studied by me and my companions is covered with rainforest and lies to the north of the highlands of Alta Verapaz and to the south of the savannas of central El Petén. A few specimens of amphibians and reptiles were obtained in this area in 1935 by C. L. Hubbs and Henry van der Schalie; this collection, reported on by Stuart (1937), contained only one species, _Cochranella fleischmanni_, not present in our collection of 77 species and 617 specimens.

Acknowledgments

I am grateful to L. C. Stuart of the University of Michigan, who made the initial arrangements for our work in El Petén, aided me in the identification of certain specimens, and helped in the preparation of this report. J. Knox Jones, Jr. and John Wellman were able field companions, who added greatly to the number of specimens in the collection. In Guatemala, Clark M. Shimeall and Harold Hoopman of the Ohio Oil Company of Guatemala made available to us the facilities of the company's camps at Chinajá and Toocog. Alberto Alcain and Luis Escaler welcomed us at Chinajá and gave us every possible assistance. Juan Monteras and Antonio Aldaña made our stay at Toocog enjoyable and profitable. During our visits to southern El Petén, Julio Bolón C. worked for us as a collector, and between March and June he collected and saved many valuable specimens; his knowledge of the forest and its inhabitants was a great asset to our work. Jorge A. Ibarra, Director of the Museo Nacional de Historia Natural in Guatemala assisted us in obtaining necessary permits and extended other kindnesses. To all of these people I am indebted for the essential parts that they played in the completion of this study.

Field work in the winter of 1960 was made possible by funds from the American Heart Association for the purposes of collecting mammalian hearts. My field work in the summer of 1960 was supported by a grant from the Graduate Research Fund of the University of Kansas.

DESCRIPTION OF THE AREA

A vast lowland region stretches northward for approximately 700 kilometers from the highlands of Guatemala to the Gulf of Mexico. The northern two-thirds of this low plain is bordered on three sides by seas and forms the Yucatán Peninsula. The lowlands at the base of the Yucatán Peninsula make up the Departamento El Petén of Guatemala. The area with which this report is concerned consists of the south-central part of El Petén.

Physiography

Immediately south of Chinajá is a range of hills, the Serrania de Chinajá, having an almost due east-west axis and a crest of about 600 meters above sea level. South of the Serrania de Chinajá are succeedingly higher ridges building up to the Meseta de Cobán and Sierra de Pocolha and eventually to the main Guatemalan highlands. The northern face of the Serrania de Chinajá is a fault scarp dropping abruptly from about 650 meters at the crest to about 140 meters at the base. From the base of the Serrania de Chinajá northward to the Río de la Pasión at Sayaxché the terrain is gently rolling and has a total relief of about 50 meters. North of the Río de la Pasión is a low dome reaching an elevation of 170 meters at La Libertad; see Stuart (1935:12) for further discussion of the physiography of central El Petén. The rocks in southern El Petén are predominately Miocene marine limestones; there are occasional pockets of Pliocene deposits. There is little evidence of subterranean solution at Chinajá, but northward in central El Petén karsting is common. The upper few inches of soil is humus rich in organic matter; below this is clay.

Climate

The climate of El Petén is tropical with equable temperatures throughout the year. Temperatures at Chinajá varied between a night-time low of 65° F. and a daytime high of 91° F. during the time of our visits. In the Köppen system of classification the climate at Chinajá and Toocog is Af. Rain falls throughout the year, but there is a noticeable dry season. To anyone who has traveled from south to north in El Petén and the Yucatán Peninsula, it is obvious from the changes in vegetation that there is a decrease in rainfall from south to north. There is a noticeable difference between Chinajá and Toocog. Although rainfall data are not available for Chinajá and Toocog, there are records for nearby stations (Sapper, 1932). At Paso Caballos on the Río San Pedro about 40 kilometers northwest of Toocog the average annual rainfall amounts to 1620 mm.; the driest month is March (21 mm.), and the wettest months are June (269 mm.) and September (265 mm.). At Cubilquitz, Alta Verapaz, about 35 kilometers south-southwest of Chinajá and at an elevation of 300 meters, the average annual rainfall is 4006 mm.; the driest month is March (128 mm.), and the wettest months are July (488 mm.) and October (634 mm.).

During the 18 days in February and March, 1960, that we kept records on the weather at Chinajá moderate to heavy showers occurred on seven days. During our stay there in June and July rain fell every day, as it did in Toocog. However, during the week spent at Toocog in March no rain fell.

Vegetation

The vegetation of northern and central El Petén has been studied by Lundell (1937), who made only passing remarks concerning the plants of the southern part of El Petén. No floristic studies have been made there. The following remarks are necessarily brief and are intended only to give the reader a general picture of the forest. I have included names of a few of the commoner trees that I recognized.

Chinajá is located in a vast expanse of unbroken rainforest. In this forest there is a noticeable stratification of the vegetation. Three strata are apparent; in the uppermost layer the tops of the trees are from 40 to 50 meters above the ground. The spreading crowns of the trees and the interlacing vines form a nearly continuous canopy over the lower layers. Among the common trees in the upper stratum are _Calophyllum brasiliense_, _Castilla elastica_, _Cedrela mexicana_, _Ceiba pentandra_, _Didalium guianense_, _Ficus_ sp., _Sideroxylon lundelli_, _Swietenia macrophylla_, and _Vitex_ sp. (Pl. 1, fig. 1). The middle layer of trees have crowns about 25 meters above the ground; these trees in some places where the upper canopy is missing form the tallest trees in the forest. This is especially true on steep hillsides. Common trees in the middle layer include _Achras zapote_, _Bombax ellipticum_, _Cecropia mexicana_, _Orbignya cohune_, and _Sabal_ sp. The lowermost layer reaches a height of about 10 meters; in many places in the forest this layer is absent. Common trees in the lower stratum include _Crysophila argentea_, _Cymbopetalum penduliflorum_, _Casearia_ sp., and _Hasseltia dioica_.

The ground cover is sparce; apparently only a few small herbs and ferns live on the heavily shaded forest floor. Important herpetological habitats include the leaf litter, rotting stumps, and rotting tree trunks on the forest floor and the buttresses of many of the gigantic trees, especially _Ceiba pentandra_ (Pl. 2). Epiphytes, especially various kinds of bromeliads, are common. Most frequently these are in the trees in the upper and middle strata.

At Toocog there is sharp break between savanna and forest (Pl. 7, fig. 2). The forest is noticeably drier and more open than at Chinajá (Pl. 9). The crowns of the trees are lower, and there is no nearly continuous canopy between 40 and 50 meters above the ground. Although _Swietenia macrophylla_ and other large trees occur, they are less common than at Chinajá. Especially common at Toocog are _Achras zapote_, _Brosimum alicastrum_, and various species of _Ficus_.

GAZETTEER

The localities from which specimens were obtained are cited below and shown on the accompanying map (Fig. 1).

Chinajá.--Lat. 16° 02´, long. 90° 13´, elev. 140 m. Camp of the Ohio Oil Company of Guatemala and formerly a small settlement. On some maps Chinajá is located just to the north of the Alta Verapaz--El Petén boundary; recent surveys place the location just to the south of the imaginary line through the rainforest. Field work was conducted in the immediate vicinity of the camp, on the lower slopes of the Serrania de Chinajá, and at several sites to the northwest and north-northwest of Chinajá, where the forest was being cleared. The entire area supports rainforest.

La Libertad.--Lat. 16° 47´, long. 90° 07´, elev., 170 m. A town on the savannas in central El Petén; although we collected there in the rainy season, the specimens obtained on the savannas are not included in this report.

Paso Subín.--Lat. 16° 38´, long. 90° 12´, elev. 90 m. A small settlement on the Río Subín, a tributary of the Río de la Pasión. Specimens were obtained in rainforest in the immediate vicinity of the settlement.

Río de la Pasión.--A large river flowing northward through southern El Petén and thence westward into the Río Usumacinta. Specimens were obtained along the river between the Río Subín and Sayaxché.

Río San Román.--A river flowing northward in south-central El Petén to the Río Salinas (Usumacinta). We collected along the river at a place about 16 kilometers north-northwest of Chinajá, approximately at Lat. 16° 10´, long. 90° 17´, elev. 110 m. In the dry season the river was clear; it is surrounded by rainforest.

Sayaxché.--Lat. 16° 31´, long. 90° 09´, elev. 80 m. A town on the southern bank of the Río de la Pasión. Specimens were obtained in the rainforest and in cleared areas in the immediate vicinity of the town.

Toocog (formerly Sojío).--Lat. 16° 41´, long. 90° 02´, elev. 140 m. A camp of the Ohio Oil Company of Guatemala located at the rainforest-savanna edge, 15 kilometers southeast of La Libertad. Although we collected on the savannas as well as in the forest, especially to the east of the camp, only species obtained in the forest are considered in this report.

THE HERPETOFAUNA OF THE RAINFOREST

In presenting an account of the herpetofauna of southern El Petén three items need to be considered: (1) The composition of the fauna; (2) the ecology of the fauna; (3) the relationships of the fauna. Each of these topics is discussed briefly below. Logically a discussion of the origin of the fauna should follow, but this is being withheld for inclusion in a report on the herpetofauna of the entire El Petén by L. C. Stuart and the author; at that time the above topics will be expanded to cover the herpetofauna of the whole region.

Composition of the Fauna

TABLE 1.--COMPOSITION OF THE HERPETOFAUNA IN SOUTHERN EL PETÉN, GUATEMALA.

=============+============+============+============ Group | Families | Genera | Species -------------+------------+------------+------------ Gymnophiona | (1)[A] | (1) | (1) Caudata | 1 | 1 | 2 Salientia | 6 | 10 (1) | 19 (1) Crocodilia | 1 | 1 | 1 Testudines | 4 | 7 | 8 Sauria | 6 | 13 (1) | 19 (1) Serpentes | 4 | 21 (7) | 29 (10) +------------+------------+------------ Total | 22 (1) | 53 (10) | 78 (13) -------------+------------+------------+------------

[Footnote A: Numbers in parenthesis indicate the number of additional taxa that probably occur.]

A total of 78 species of amphibians and reptiles has been found in the rainforests in southern El Petén; a break down into families and genera is given in table 1. Another 13 species probably occur in southern El Petén (see Hypothetical List of Species). The fauna primarily is composed of typical humid lowland forest inhabitants, such as:

_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_

PLATE 7

PLATE 8

PLATE 9

PLATE 10

Ecology of the Herpetofauna

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.

Of the six species of _Anolis_, all except _A. sericeus_ are typically found in humid forests. _Anolis sericeus sericeus_ is poorly represented in the collections from southern El Petén, where it may be in competition with _Anolis limifrons rodriguezi_ that resembles _Anolis s. sericeus_ in size, coloration, and habits. Therefore, _Anolis sericeus sericeus_ is excluded from the following discussion. The common terrestrial species is _Anolis humilis uniformis_; sometimes this small species perches or suns on the bases of small trees or buttresses of some large trees. When disturbed it takes to the ground and seeks cover in the leaf litter or beneath logs or palm fronds. _Anolis lemurinus bourgeaei_ is about twice the size of _Anolis humilis uniformis_ and is usually observed on buttresses of large trees or on the lower two meters of tree trunks. Individuals were seen foraging on the ground along with _Anolis humilis uniformis_. At no time were _Anolis lemurinus bourgeaei_ observed to ascend the trunks of large trees; they always took refuge near the bases of trees. _Anolis limifrons rodriguezi_ is found on the stems and branches of bushes. It is a small species that sometimes is observed on the ground but was never seen ascending large trees. _Anolis capito_ is about the same size as _Anolis lemurinus bourgeaei_ and lives on the trunks of large trees. In the tops of the trees lives a large green species, _Anolis biporcatus_.

Similar segregation habitatwise can be demonstrated for other members of the herpetofauna. The avoidance of interspecific competition in feeding is well illustrated by three species of snakes that probably are the primary ophidian predators on frogs. _Drymobius margaritiferus margaritiferus_ is diurnal and terrestrial; it feeds on frogs at the edges of breeding ponds by day. Also during the day _Leptophis mexicanus mexicanus_ feeds on frogs in bushes and trees. At night the activities of both of these species is replaced by those of _Leptodeira septentrionalis polysticta_, which not only feeds on the frogs in the trees and bushes, but descends to the ground and even enters the water in search of food.

From the examples discussed above, the importance of the three dimensional aspect of the rainforest is apparent. The presence of a large and diverse habitat above the ground is of great significance in the rainforest, for of the non-aquatic components of the herpetofauna in the rainforests of southern El Petén, 42 per cent of the species spend at least part of their lives in the bushes and trees. Another important part of the forest is the subterranean level--the rich mulch, underground tunnels, and rotting subterranean vegetation. Of the 78 species of amphibians and reptiles in southern El Petén, seven are primarily fossorial, and half-a-dozen others are secondarily fossorial. Probably the fossorial members of the fauna are the least well represented in the collection, for such widespread species as _Dermophis mexicanus mexicanus_, _Rhadinaea decorata decorata_ and _Tantilla schistosa schistosa_ were expected, but not found.

In the following discussion of the ecological distribution of amphibians and reptiles in the rainforest I have depended chiefly on my observations made in southern El Petén, but have taken into consideration observations made on the same species in other regions, together with reports from other workers. The reader should keep in mind that the evidence varies from species to species. Of some species I have observed only one animal in the field; of others, I have seen scores and sometimes hundreds of individuals. For species on which I have few observations or rather inconclusive evidence, the circumstance of inadequate data is mentioned.

In analyzing the ecological distribution within the forest, it is convenient to recognize five subdivisions (habitats); each is treated below as a unit.

1. AQUATIC.--This habitat includes permanent streams and rivers (Pl. 10, fig. 1), some of which are clear and others muddy. In the rainy season temporary ponds form in depressions on the forest floor (Pl. 10, fig. 2); these are important as breeding sites for many species of amphibians. Aquatic members of the herpetofauna are here considered to be those species that either spend the greatest part of their lives in the water or usually retreat to water for shelter. Seven species of turtles and one crocodilian are aquatic. Of these, _Dermatemys mawi_, _Staurotypus triporcatus_, and _Pseudemys scripta ornata_ inhabit clear water, whereas _Chelydra rossignoni_, _Claudius angustatus_, _Kinosternon acutum_, and _K. leucostomum_ inhabit muddy water. _Crocodylus moreleti_ apparently inhabits both clear and muddy water, for in the dry season it lives along the clear rivers, but in the rainy season inhabits flooded areas in the forest as well.

2. AQUATIC MARGIN.--Extensive marshes were lacking in the part of southern El Petén that I visited; consequently, the aquatic margin habitat is there limited to the edges of rivers and borders of temporary ponds. _Bufo marinus_, _Rana palmipes_, and _Rana pipiens_ are characteristic inhabitants of the aquatic margin, although in the rainy reason _Bufo marinus_ often is found away from water. Observations indicate that _Tretanorhinus nigroluteus lateralis_ inhabits the margins of ponds and streams and actually spends considerable time in the water. Although _Iguana iguana rhinolopha_ is arboreal, it lives in trees along rivers, into which it plunges upon being disturbed. Species included in this category are those that customarily spend most of their lives at the edge of permanent water. Frogs and toads that migrate to the water for breeding and the snakes that prey on the frogs at that time are not assigned to the aquatic-margin habitat.

3. FOSSORIAL.--Characteristic inhabitants of the mulch on the forest floor are _Bolitoglossa moreleti mulleri_, _Lepidophyma flavimaculatum flavimaculatum_, _Scincella cherriei cherriei_, _Ninia sebae sebae_, _Pliocercus euryzonus aequalis_, and _Micrurus affinis apiatus_. Other species of snakes that spend most of their lives above ground often forage in the mulch layer; among these are _Coniophanes bipunctatus biserialis_, _Coniophanes fissidens fissidens_, _Coniophanes imperialis clavatus_, _Lampropeltis doliata polyzona_, and _Stenorrhina degenhardti_. Among the amphibians, at least _Hypopachus cuneus nigroreticulatus_, _Eleutherodactylus rostralis_, and _Syrrhophus leprus_ are known to seek shelter in the mulch.

4. TERRESTRIAL.--One turtle, _Geoemyda areolata_, is primarily terrestrial. Among the lizards, conspicuous terrestrial species are _Anolis humilis uniformis_ and _Ameiva festiva edwardsi_; _Anolis lemurinus bourgeaei_ and _Basiliscus vittatus_ spend part of their lives on the ground, but also live on trees and in bushes. _Eumeces schwartzei_ and _E. sumichrasti_ apparently are terrestrial. The only terrestrial lizard that is nocturnal is _Coleonyx elegans elegans_, which by day hides in the leaf litter or below ground. Nocturnal amphibians that are terrestrial include _Bufo marinus_, _Bufo valliceps valliceps_, _Eleutherodactylus rugulosus rugulosus_, _Syrrhophus leprus_, and _Hypopachus cuneus nigroreticulatus_. A large number of active diurnal snakes are terrestrial; these include _Boa constrictor imperator_, _Clelia clelia clelia_, _Dryadophis melanolomus laevis_, _Drymarchon corais melanurus_, _Drymobius margaritiferus margaritiferus_, _Pseustes poecilonotus poecilonotus_, and _Spilotes pullatus mexicanus_. Nocturnal terrestrial snakes include three kinds of _Bothrops_ (_B. atrox asper_, _B. nasutus_, and _B. nummifer nummifer_), all of which seem to be equally active by day.

5. ARBOREAL.--In this habitat the third dimension (height) of the rainforest probably is the most complex insofar as the inter-relationships of species and ecological niches are concerned. I have attempted to categorize species as to microhabitats within the arboreal habitat; in so doing, I recognize four subdivisions--bushes, tree trunks, tree tops, and epiphytes.

Bush inhabitants include several species of lizards and snakes, all of which have rather elongate, slender bodies, and long tails. Common bush-inhabitants in southern El Petén are _Anolis limifrons rodriguezi_, _Basiliscus vittatus_, _Laemanctus deborrei_, _Leptophis mexicanus mexicanus_, and _Oxybelis aeneus aeneus_. All of these are diurnal, and all but _Laemanctus_ have been observed sleeping on bushes at night.

Tree-trunk inhabitants include five species of lizards. _Thecadactylus rapicaudus_ lives on the trunks of large trees; _Sphaerodactylus lineolatus_ lives beneath the bark on dead trees and on corozo palms. _Anolis lemurinus bourgeaei_ lives on the bases and buttresses of large trees, from which it often descends to the ground. _Corythophanes cristatus_ and _Anolis capito_ were found only on tree trunks and large vines.

The least information is available for the species living in the tree tops. The following species were obtained from tops of trees when they were felled, or have been observed living in the tree tops: _Anolis biporcatus_, _Iguana iguana rhinolopha_, _Celestus rozellae_, _Leptodeira septentrionalis polysticta_, _Leptophis ahaetulla praestans_, _Sibon dimidiata dimidiata_, and _Sibon nebulata nebulata_.

Epiphytes, especially the bromeliads, provide refuge for a variety of tree frogs and small snakes. Of the tree frogs, _Hyla picta_, _Hyla staufferi_, _Phyllomedusa callidryas taylori_, _Similisca baudini_, and _Similisca phaeota cyanosticta_ have been found in bromeliads; other species probably occur there. Among the snakes, _Imantodes cenchoa leucomelas_, _Leptodeira frenata malleisi_, _Leptodeira septentrionalis polysticta_, _Sibon dimidiata dimidiata_, and _Sibon nebulata nebulata_ are frequent inhabitants of bromeliads; all of these snakes are nocturnal.

Relationships of the Fauna

Most of the 78 species of amphibians and reptiles definitely known from the rainforest in southern El Petén have extensive ranges in the Atlantic lowlands of southern México and Central America; many extend into South America. Sixty-two (80%) of the species belong to this group having extensive ranges in Middle America. Three species (_Syrrhophus leprus_, _Leptodeira frenata_, and _Kinosternon acutum_) are at the southern limits of their distributions in southern El Petén and northern Alta Verapaz, whereas _Eleutherodactylus rostralis_ and _Thecadactylus rapicaudus_ are at the northern and western limits of their distributions in El Petén. Nine (11%) species have the center of their distributions in El Petén and the Yucatán Peninsula; representatives of this group include _Claudius angustatus_, _Dermatemys mawi_, _Laemanctus deborrei_, and _Eumeces schwartzei_.

In determining a measure of faunal resemblance, I have departed from the formulae discussed by Simpson (1960) and have analyzed the degree of resemblance by the following formula used to calculate an index of faunal relationships:

C (2) / (N_{1} + N_{2}) = R, where

C = species common to both faunas.

N_{1} = number of species in the first fauna.

N_{2} = number of species in the second fauna.

R = degree of relationships (when R = 1.00, the faunas are identical; when R = 0, the faunas are completely different).

The herpetofauna of southern El Petén has been compared with that in the Tikal-Uaxactún area (Stuart, 1958), that in the humid lowlands of Alta Verapaz (Stuart, 1950, plus additional data), and that in the Mexican state of Yucatán (Smith and Taylor, 1945, 1948, and 1950). The herpetofaunas of lowland Alta Verapaz and Yucatán are the largest, having respectively 94 and 91 species, where as there are 78 species known from southern El Petén and 64 from the Tikal-Uaxactún area. An analysis of faunal relationships (Table 2) shows that the faunas of the rainforests of southern El Petén and lowland Alta Verapaz are closely related. The relationships between these two areas and the Tikal-Uaxactún area in northern El Petén is notably less. Apparently the biggest faunal changes take place between southern El Petén and the Tikal-Uaxactún area, and between the latter and Yucatán. As stated by Stuart (1958:7) the Tikal-Uaxactún is transitional between the humid rainforests to the south and the dry outer end of the Yucatán Peninsula. The transitional nature of the environment is exemplified by a rather depauperate herpetofauna consisting of some species of both dry and humid environments and lacking a large fauna typical of either. Contrariwise, the continuity of the environment from southern El Petén to the lowlands of Alta Verapaz is reflected in degree of resemblance of the herpetofaunas.

TABLE 2.--INDEX OF FAUNAL RELATIONSHIPS BETWEEN SOUTHERN EL PETÉN AND OTHER REGIONS.

======================+==========+==========+==========+========== | Lowland | Southern | Tikal- | | Alta | El | Uaxactún | Yucatán | Verapaz | Petén | Area | ----------------------+----------+----------+----------+---------- Lowland Alta Verapaz | | .85 | .61 | .43 ----------------------+----------+----------+----------+---------- Southern El Petén | .85 | | .64 | .41 ----------------------+----------+----------+----------+---------- Tikal-Uaxactún Area | .61 | .64 | | .63 ----------------------+----------+----------+----------+---------- Yucatán | .43 | .41 | .63 | ----------------------+----------+----------+----------+----------

Most of the species of amphibians and reptiles found in southern El Petén are found in humid tropical forests from the Isthmus of Tehuantepec southeastward on the Atlantic lowlands well into Central America.

ACCOUNTS OF SPECIES

In the following pages various aspects of the occurrence, life histories, ecology, and variation of the species of amphibians and reptiles known from southern El Petén are discussed. Only _Cochranella fleischmanni_ reported by Stuart (1937) from Río Subín at Santa Teresa was not collected by us and is excluded. Because more worthwhile information was gathered for some species than others, the length and completeness of the accounts vary. All specimens listed are in the Museum of Natural History at the University of Kansas, to which institution all catalog numbers refer. Preceding the discussion of each species is an alphabetical list of localities from which specimens were obtained; numbers after a locality indicate the number of specimens obtained at each locality.

=Bolitoglossa dofleini= (Werner)

Chinajá, 1.

An adult female having minute ovarian eggs has a snout-vent length of 81 mm., a tail length of 59 mm., 13 costal grooves, two intercostal spaces between adpressed toes, 38-35 vomerine teeth in irregular rows forming a broad arch from a point posterolaterad to the internal nares to a point near the anterior edge of the parasphenoid teeth, and 43-44 maxilliary-premaxillary teeth. In life the dorsum was rusty brown with irregular black and orange spots and streaks. The flanks were bluish gray with black in the costal grooves and creamy tan flecks along the ventral edge of the flank. The belly and underside of the tail were yellowish tan with dark brown spots laterally. The limbs were orange proximally and black distally; the pads of the feet were bluish black. The dorsal and lateral surfaces of the tail were yellowish orange with black spots. The iris was grayish yellow.

Stuart (1943:17) reported this species from Finca Volcán, Alta Verapaz. He diagnosed his specimens as having 13 costal grooves and two or three intercostal spaces between adpressed toes. He stated that the vomerine teeth were about 12 in number and that in life the dorsum was mottled gray and black, the sides gray and brown, and the undersurfaces uniformly dark gray. These specimens differ noticeably from the individual from Chinajá in the number of vomerine teeth and in coloration.

In August, 1961, I obtained a specimen of _Bolitoglossa dofleini_ at Finca Los Alpes, Alta Verapaz, approximately 13 kilometers airline south-southwest of Finca Volcán and at approximately the same elevation. Although the salamander was dead when found, it obviously was more heavily pigmented than the individual from Chinajá. The belly was bluish gray with black spots laterally; the dorsum was dull brownish gray with some brownish red streaks. The specimen is a female having small ovarian eggs, a snout-vent length of 90 mm., 13 costal grooves, and two intercostal spaces between adpressed limbs. There are 28-29 vomerine teeth, more than twice as many as in specimens from Finca Volcán (Stuart, 1943:17), but noticeably fewer than in the specimen from Chinajá.

The presence of this species at Chinajá lends support to the idea that the specimen from the Río de la Pasión listed by Brocchi (1882:116) also is _Bolitoglossa dofleini_. Furthermore, the confirmed presence of this species in the lowlands of El Petén suggests that there may be genetic connection between _B. dofleini_ in the Alta Verapaz and _B. yucatana_ in the Yucatán Peninsula. _Bolitoglossa yucatana_ differs from _B. dofleini_ in having five intercostal spaces between adpressed toes and in having a different color pattern. Both are robust species having no close relationships to other species of _Bolitoglossa_ in northern Central America.

The specimen from Chinajá was found in water in the axil of a large elephant-ear plant (_Xanthosoma_) by day in March. Its stomach contained fragments of beetles and a large roach. The natives did not know salamanders and had no name for them.

=Bolitoglossa moreleti mulleri= (Brocchi)

Chinajá, 2; Río San Román, 1.

One specimen is a female having a snout-vent length of 80 mm., a tail length of 82 mm., and a total length of 162 mm. It contains 63 large eggs, the largest of which has a diameter of about three millimeters. This specimen has 13 costal grooves, four intercostal spaces between adpressed toes, and 12-13 vomerine teeth. A juvenile having a snout-vent length of 39 mm. and a tail length of 33 mm. has 12 costal grooves, three intercostal spaces between adpressed toes, and 8-8 vomerine teeth. In life these salamanders were uniformly dull brownish black above with a dull creamy yellow irregular dorsal stripe beginning on the occiput and continuing onto the tail. There are no yellow or orange streaks or flecks on the head or limbs. The specimen from the Río San Román was taken from the stomach of a _Pliocercus euryzonus aequalis_ and has not been studied in detail, because of its poor condition.

The present specimens show no tendency for the development of a broad irregular dorsal band that encloses black spots or forms irregular dorsolateral stripes, as is characteristic of _B. moreleti mexicanus_, a subspecies that has been reported from La Libertad (Stuart, 1935:35) and Piedras Negras (Taylor and Smith, 1945:545) in El Petén, and from Xunantunich, British Honduras (Neill and Allen, 1959:20).

Schmidt (1936:151) and Stuart (1943:13) found _B. moreleti mulleri_ in bromeliads at Finca Samac, Alta Verapaz. Taylor and Smith's (1945:545) and Neill and Allen's (1959:20) specimens of _B. moreleti mexicanus_ were obtained from bromeliads, but Neill and Allen (_loc. cit._) stated that the natives in British Honduras said that they had found salamanders beneath rubbish on the forest floor. My specimens were obtained from beneath logs on the forest floor in the rainy season. Possibly in drier environments the species characteristically inhabits bromeliads, at least in the dry season.

=Bufo marinus= (Linnaeus)

Chinajá, 3; 10 km. NNW of Chinajá, 1; 11 km. NNW of Chinajá, 1.

During both visits to Chinajá this large toad was breeding in a small permanent pond in the camp. During the day the toads took refuge in crevices beneath the buildings or beneath large boulders by the pond. At dusk from four to ten males congregated at the pond and called. Tadpoles of this species were in the pond in March and in July. One juvenile was found beneath a rock in the forest, and another was on the forest floor by day.

The natives' name for this species and the following one is _sapo_.

=Bufo valliceps valliceps= Wiegmann

Chinajá, 52; Río San Román, 8; Sayaxché, 2; Toocog, 1.

This is one of the most abundant, or at least conspicuous, amphibians inhabiting the forest. Breeding congregations were found on February 24, March 2, March 11, and June 27. At these times the toads were congregated at temporary ponds in the forest or along small sluggish streams. Throughout the duration of both visits to Chinajá individual males called almost nightly at the permanent pond at the camp.

The variation in snout-vent length of 20 males selected at random is 56.7 to 72.5 mm. (average, 64.8 mm.). Two adult females have snout-vent lengths of 80.4 and 87.6 mm. In all specimens the parotid glands are somewhat elongated and not rounded as in _Bufo valliceps wilsoni_ (see Baylor and Stuart, 1961:199). My observations on the condition of the cranial crests of the toads in El Petén agree with the findings of Baylor and Stuart (_op. cit._:198) in that hypertrophied crests are usual in large females. In the shape of the parotids and nature of the cranial crests the specimens from El Petén are like those from the Isthmus of Tehuantepec in México. As I pointed out (1960:53), the validity of the subspecies _Bufo valliceps macrocristatus_, described from northern Chiapas by Firschein and Smith (1957:219) and supposedly characterized by hypertrophied cranial crests, is highly doubtful.

In the toads from El Petén the greatest variation is in coloration. The dorsal ground-color varies from orange and rusty tan to brown, yellowish tan, and pale gray. In some individuals the flanks and dorsum are one continuous color, whereas in others a distinct dorsolateral pale colored band separates the dorsal color from dark brown flanks. In some individuals the venter is uniform cream color, in others it bears a few scattered black spots, and in still others there are many spots, some of which are fused to form a black blotch on the chest. In breeding males the vocal sac is orange tan. All specimens have a coppery red iris.

Aside from the breeding congregations, active toads were found on the forest floor at night; a few were there by day. Some individuals were beneath logs during the day.

=Eleutherodactylus rostralis= (Werner)

Chinajá, 10.

Because of the multiplicity of names and the variation in coloration, the small terrestrial _Eleutherodactylus_ in southern México and northern Central America are in a state of taxonomic confusion. Stuart (1934:7, 1935:37, and 1958:17) referred specimens from El Petén to _Eleutherodactylus rhodopis_ (Cope). Stuart (1941b:197) described _Eleutherodactylus anzuetoi_ from Alta Verapaz and El Quiché, Guatemala, suggested that the new species was an upland relative of _Eleutherodactylus rostralis_ (Werner), and used that name for the frogs that he earlier had referred to _Eleutherodactylus rhodopis_. Dunn and Emlen (1932:24) placed _E. rostralis_ in the synonymy of _E. gollmeri_ (Peters). Examination of series of these frogs from southern México, Guatemala, and Costa Rica causes me to think that there are four species; these can be distinguished as follows:

_E. rhodopis._--No web between toes; one tarsal tubercle; tibiotarsal articulation reaches to nostril; iris bronze in life.

_E. anzuetoi._--No web between toes; a row of tarsal tubercles; tibiotarsal articulation reaches to tip of snout; color of iris unknown.

_E. rostralis._--A vestige of web between toes; no tarsal tubercles; tibiotarsal articulation reaches snout or slightly beyond; iris coppery red in life.

_E. gollmeri._--A vestige of web between toes; no tarsal tubercles; tibiotarsal articulation reaches well beyond snout; iris coppery red in life.

The presence of webbing between the toes, the absence of tarsal tubercles, and the coppery red iris distinguish _E. rostralis_ and _E. gollmeri_ from the other species. Probably _E. rostralis_ and _E. gollmeri_ are conspecific, but additional specimens are needed from Nicaragua and Honduras to prove conspecificity. On the other hand, the characters of the frogs from Chinajá clearly show that they are related to _E. gollmeri_ to the south and not to _E. rhodopis_ to the north in México.

At Chinajá, _Eleutherodactylus rostralis_ was more abundant than the few specimens indicate, for upon being approached the frogs moved quickly and erratically, soon disappearing in the leaf litter on the forest floor. Most of the specimens were seen actively moving on the forest floor in the daytime; one was found beneath a rock, and one was on the forest floor at night.

=Eleutherodactylus rugulosus rugulosus= (Cope)

Chinajá, 2; 15 km. NW of Chinajá, 4.

These frogs were found on the forest floor by day. With the exception of one female having a snout-vent length of 69.5 mm., all are juveniles. The apparent rarity of this species at Chinajá may be due to the absence of rocky streams, a favorite habitat of this frog. The local name for this frog is _sapito_, meaning little toad.

=Leptodactylus labialis= (Cope)

Toocog, 1.

One juvenile having a snout-vent length of 16.4 mm. was found at night beside a pond in the forest. The scarcity of the species of _Leptodactylus_ in the southern part of El Petén probably is due to the lack of permanent marshy ponds.

=Leptodactylus melanonotus= (Hallowell)

Sayaxché, 1.

One individual was found beneath a rock beside a stream in the forest. The local name is _ranita_, meaning little frog.

=Syrrhophus leprus= Cope

Chinajá, 2; 15 km NW of Chinajá, 1.

An adult female having a snout-vent length of 27.5 mm. was found on the forest floor by day. Two juveniles having snout-vent lengths of 15.5 and 19.0 mm. were beneath rocks on the forest floor. The specimens are typical of the species as defined by Duellman (1958:8).

=Hyla ebraccata= Cope

Toocog, 66.

This small tree frog congregated in large numbers at a forest pond at Toocog. Between June 30 and July 2 we collected specimens and observed the breeding habits of this and other species at the pond. Calling males were distributed around the pond, where they called from low herbaceous vegetation at the edge of the pond or from plants rising above the water. Calling commenced at dusk and continued at least into the early hours of the morning. On one occasion a female was observed at a distance of about 50 centimeters away from a calling male sitting on a blade of grass. The female climbed another blade of grass until she was about eight centimeters away from the male, at which time he saw her, stopped calling, jumped to the blade of grass on which she was sitting and clasped her. Clasping pairs were observed on blades of grass and leaves of plants above the water; most pairs were less than 50 centimeters above the surface of the pond.

The eggs are deposited on the dorsal surfaces of leaves above the water. All eggs are in one plane (a single layer) on the leaf. External membranes are barely visible, as the eggs consist of a single coherent mass. Eggs in the yolk plug stage have diameters of 1.2 to 1.4 mm. Seventeen eggs masses were found; these contained from 24 to 76 (average 44) eggs. The jelly is extremely viscous and tacky to the touch. At time of hatching the jelly becomes less viscous; the tadpoles wriggle until they reach the edge of the leaf and drop into the water.

Eleven tadpoles were preserved as they hatched; these have total lengths of 4.5 to 5.0 (average 4.77) mm. Hatchling tadpoles are active swimmers and have only a small amount of yolk. The largest tadpoles preserved have total lengths of 13.0 and 13.5 mm. At this size distinctive sword-tail and bright coloration have developed.

Description of fully developed tadpole (KU 59986): Total length, 13.5 mm.; tail-length, 8.4 mm., 62 per cent of total length. Snout, in dorsal view, bluntly rounded; in lateral view less bluntly rounded; body depressed; head flattened; mouth terminal; eye large, its diameter 25 per cent of length of body; nostrils near tip of snout and directed anteriorly; spiracle sinistral and situated postero-ventrad to eye; cloaca median. Tail-fin thrice depth of tail-musculature, which extends beyond posterior end of tail-fin giving sword-tail appearance (Fig. 2). In life, black stripe on each side of body and on top of head; black band on anterior part of tail and another on the posterior part; body and anterior part of tail creamy yellow; dark red band between black bands on tail. Mouth terminal, small, its width about one-fifth width of body; fleshy ridge dorsally and ventrally; row of small papillae on ventral lip; no lateral indentations of lips; upper beak massive, convex, and finely serrate; lower beak small and mostly concealed behind upper; no teeth (Fig. 3).

=Hyla loquax= Gaige and Stuart

Toocog, 14.

These specimens were found at night when they were calling from low vegetation in a forest pond. Most of the frogs were several meters away from the edge of the pond. Although two clasping pairs were found, we obtained no eggs or tadpoles referable to this species.

=Hyla microcephala martini= Smith

Chinajá, 1; Toocog, 21.

The specimen from Chinajá was calling from a small bush at the edge of a temporary grassy pond in a clearing in the forest. At Toocog this species was closely associated with _Hyla ebraccata_; males were calling from herbaceous vegetation in and around the forest pond. These frogs were not so abundant in the forest at Toocog as they were around ponds on the savanna at La Libertad.

=Hyla picta= (Günther)

Toocog, 8.

This small tree frog was calling from herbs in a pond in the forest on June 30 and July 2. The voice is weak; probably greater numbers of males were present than are indicated by the few specimens collected, for the din from the more vociferous species made it impossible to hear _Hyla picta_ unless one was calling close by.

=Hyla staufferi= Cope

Chinajá, 1.

This individual was calling from a low bush in the clearing at Chinajá. None was found in the pond in the forest at Toocog. Stuart (1935:38) and Duellman (1960:63) noted that _Hyla staufferi_ breeds early in the rainy season. Nevertheless, I think early breeding habits do not account for the near absence of this species in our collections from southern El Petén. In early July, 1960, a few individuals were heard at a pond on the savanna at La Libertad. In mid-July of the same year they were calling sporadically from temporary ponds in the lower Motagua Valley. Possibly the individual collected at Chinajá was accidentally transported there in cargo from Toocog, from which camp at the edge of the savanna planes fly to Chinajá weekly. My observations on this species throughout its range in México and Central America indicate that it inhabits savannas and semi-arid forests and usually is absent from heavy rainforest. Stuart (1948:34) obtained this species at Cubilquitz in the lowlands of Alta Verapaz.

=Phyllomedusa callidryas taylori= Funkhouser

Toocog, 25.

Between June 30 and July 2 this species was abundant at a pond in the forest at Toocog. Calling males were as high as five meters in bushes and trees around the pond. At dusk males were observed descending a vine-covered tree at the edge of the pond; this strongly suggests that the frogs retreat to this tree and others like it for diurnal seclusion. Clasping pairs were found on branches and leaves above the water. The eggs are deposited in clumps usually on vertical leaves, but sometimes on horizontal leaves or on branches, vines, and aerial roots above the water. Twenty-six clutches of eggs contained from 14 to 44 (average 29) eggs. In a clutch in which the eggs are in yolk plug stage the average diameter of the embryos is 2.3 mm. and that of the vitelline membranes, 3.4 mm. Most of the eggs are in the external part of the gelatinous mass; the jelly is clear. The yolk is pale green, and the animal pole is brown. As development ensues, the yolk becomes yellow and the embryo first dark brown and then pale grayish tan. Upon hatching the tadpoles wriggle free of the jelly and drop into the water. One clutch of 19 eggs was observed to hatch in three minutes. Apparently, on dropping into the water the hatchling tadpoles go to the bottom of the pond, for one or two minutes pass from the time they enter the water until they reappear near the surface. The average total length of seven hatchling tadpoles is 7.4 mm. There is a moderate amount of yolk, but this does not form a large ventral bulge. Large tadpoles congregate in the sunny parts of the pond, where they were observed just beneath the surface. Many had their mouths at the surface. Except for constant fluttering of the tip of the tail, they lie quietly with the axis of the body at an angle of about 45 degrees with the surface of the water.

Description of tadpole (KU 60006): total length, 24.5 mm.; tail-length, 15.4 mm.; body broader than deep; head moderately flattened; snout viewed from above blunt; nostrils close to snout and directed dorsally; eyes of moderate size and directed laterally; mouth directed anteroventrally; anus median; spiracle ventral, its opening just to left of midline slightly more than one-half distance from tip of snout to vent. Tail-fin slightly more than twice as deep as tail musculature, which curves upward posteriorly; tail-fin narrowly extending to tip of tail (Fig. 4). Color in life pale gray; in preservative white with scattered melanophores; tail-fin transparent.

Upper lip having single row of papillae laterally, but none medially; lower lip having single row of papillae; no lateral indentation of lips; two or more rows of papillae at lateral corners of lips; tooth-rows 2/3; second upper tooth row as long as first, interrupted medially; inner lower tooth-row as long as upper rows, interrupted medially; second and third lower rows decreasingly shorter; upper beak moderate in size and having long lateral projections; lower beak moderate in size; both beaks finely serrate (Fig. 5).

=Smilisca baudini= (Duméril and Bibron)

Chinajá, 9; 20 km. NNW of Chinajá, 42; Río de la Pasión, 1; Río San Román, 5; Sayaxché; Toocog, 2.

Individuals of this species were found at night sitting on bushes and small trees in the forest in February and March and again in June and July. One was in the axil of a leaf of a _Xanthosoma_. In June and July males were heard nearly every night. The series of specimens from 20 kilometers north-northwest of Chinajá was taken from a breeding congregation in a shallow muddy pool in the forest. Tadpoles of this species were in small, often muddy pools in the forest. To my knowledge _Smilisca baudini_ is the only hylid to breed in these pools at Chinajá, although perhaps _Smilisca phaeota_ also utilizes them. The only other amphibian at Chinajá known to breed in the pools is _Bufo valliceps valliceps_. Although two specimens were on bushes at night at Toocog, _Smilisca baudini_ was not present at the pond where five other species of hylids were breeding. Nevertheless, _Smilisca baudini_ was calling from two ponds on the savannas near La Libertad. All of the specimens from southern El Petén have yellow or yellowish white flanks and ventrolateral surfaces.

=Smilisca phaeota cyanosticta= (Smith)

Chinajá, 4; 10 km. NNW of Chinajá, 1.

All specimens were found in February and March. Those from Chinajá were obtained from _Xanthosoma_ and bromeliads; the individual from 10 kilometers north-northwest of Chinajá is an adult male that was calling from a puddle in a fallen tree on March 13. A juvenile having a snout-vent length of 34.7 mm. lacks the pale blue spots on the thighs; instead, the anterior and posterior surfaces of the thighs are bright red.

=Hypopachus cuneus nigroreticulatus= Taylor

Toocog, 1.

An adult male having a snout-vent length of 41.7 mm. was found at night on the forest floor at the edge of a temporary pond. In life the dorsum was dark brown with chocolate brown markings; the stripe on the side of the head was white; the middorsal stripe was pale orange; the belly was black and white, and the iris was a bronze color.

Characteristically this species inhabits savannas and open forest; thus, its occurrence in the rainforest at Toocog is surprising. This is the southernmost record for the species in El Petén; to the south in the highlands it is replaced by the smaller _Hypopachus inguinalis_, having rounded, instead of compressed, metatarsal tubercles.

=Rana palmipes= Spix

Chinajá, 11; 15 km. NW of Chinajá, 1; 20 km. NNW of Chinajá, 1.

With the exception of one recently metamorphosed juvenile having a snout-vent length of 30.7 mm. that was found on the forest floor by day on June 24, and one that was found beside a pool in a cave, all individuals were found at temporary woodland pools or along sluggish streams at night. The largest specimen is a female having a snout-vent length of 107 mm.

=Rana pipiens= Schreber

Chinajá, 1; 20 km. NNW of Chinajá, 1; Río San Román, 1; Toocog, 1.

All specimens were found near water at night. The largest individual is a female having a snout-vent length of 112.5 mm.

=Crocodylus moreleti= Duméril and Duméril

Chinajá, 1; Río San Román, 1.

One specimen was obtained from a quiet pool in the Río San Román at night; another was found in a small sluggish stream at Chinajá. Two large individuals were seen in tributaries to the Río San Román. On the savannas at Toocog two small individuals were obtained in the dry season, at which time the crocodiles apparently were migrating to water. The local name for this species is _lagarto_.

=Chelydra rossignoni= (Bocourt)

Chinajá, 1; 20 km. NNW of Chinajá, 1.

The paucity of specimens of _Chelydra_ from Central America has resulted in rather inadequate diagnoses of various populations. The present specimens have carapace lengths of 250 and 238 mm. and plastral lengths of 185 and 176 mm. The length of carapace/bridge ratio is 6.0 and 6.1 per cent. Each individual has four barbels, the median pair of which are extremely long. In KU 55977 the lateral pair of barbels is forked at the base. The relative length of the plastral bridge in these specimens compares favorable with the ratio (.06-.08) given by Schmidt (1946:4) for five specimens from Honduras. _Chelydra serpentina_, which may occur sympatrically with _C. rossignoni_ in some parts of Central America, has a narrower plastral bridge and only two barbels beneath the chin. Furthermore, _C. rossignoni_ and _C. osceola_ in Florida have long, flat tubercles on the dorsal and lateral surfaces of the neck, whereas _C. serpentina_ has short, round tubercles.

The specimen from Chinajá was found in a small sluggish stream; the other individual was in a muddy pool in the forest. The local name is _sambodanga_.

=Claudius angustatus= Cope

20 km. NNW of Chinajá, 1.

One specimen was unearthed from the bank of a small muddy stream by a bulldozer. This individual represents the second record for the species in Guatemala; the first was provided by specimens, likewise found in muddy waters, at Tikal (Stuart, 1958:19). The local name is _caiman_.

=Kinosternon acutum= Gray

20 km. NNW of Chinajá, 4; 30 km. NNW of Chinajá, 2.

These turtles were found on the forest floor, in small sluggish streams, and in pools in the forest. One adult male had, in life, the top of the head yellow with black spots; the stripes on the head and neck were red. Specimens were obtained both in the dry and rainy seasons. The local name for both species of _Kinosternon_ is _pochitoque_.

=Kinosternon leucostomum= Duméril and Bibron

Chinajá, 3; 15 km. NW of Chinajá, 1; 20 km. NNW of Chinajá, 2.

Individuals of this turtle were found on the forest floor and in small sluggish streams. In life most specimens had a tan or pale brown head with pinkish tan stripes on the head and neck. All individuals were obtained in February and March. No ecological differences between this species and _K. acutum_ were evident.

=Staurotypus triporcatus= (Wiegmann)

Paso Subín, 1.

This species is represented in the collection by one complete shell found on the bank of the Río Subín. The carapace has a length of 292 mm. The local name is _Guao_. Natives stated that this turtle was not uncommon in clear rivers and lakes, a habitat suggested for the species by Stuart (1958:19).

=Dermatemys mawi= Gray

Chinajá, 1; Río San Román, 4.

The record from Chinajá is based on a carapace found in a chiclero camp, where the turtle evidently had been brought for food. The four specimens from the Río San Román were obtained from edges of deep pools in clear water. In adult males the top of the head was reddish orange in life. One of the specimens from the Río San Román currently is living in the Philadelphia Zoological Gardens. The local name for this turtle is _tortuga blanca_; it is sought for its meat.

=Geoemyda areolata= (Duméril and Bibron)

Chinajá, 2.

Two specimens were obtained from dense forest at Chinajá. The local name is _mojina_.

=Pseudemys scripta ornata= (Gray)

Paso Subín, 1.

One subadult was obtained from clear water in the Río Subín. The stripes on the head and neck were yellow; there was no red "ear" on the side of the head. The stripes on the forelimbs were orange, and the ocelli on the carapace were red. The local name is _jicotea_.

=Coleonyx elegans elegans= Gray

Toocog, 1.

One adult male having a snout-vent length of 89 mm. was found beneath a log in the forest. Locally this gecko is known as _escorpión_; the natives believe it to be deadly poisonous. The use of the name _escorpión_ seems to be restricted to lizards thought to be venomous. Nearly everywhere in México and Central America some species of lizard carries this appellation. In El Petén I heard the name used only for _Coleonyx elegans_ and _Thecadactylus rapicaudus_; in the lowlands of Guerrero, México, the name is applied to geckos of the genus _Phyllodactylus_. The venomous lizards of the genus _Heloderma_ in the lowlands of western México are called _escorpiónes_. In the mountains of southern México various skinks of the genus _Eumeces_, as well as lizards of the genus _Xenosaurus_, carry the same appellation. _Abronia_ in the mountains of México and _Gerrhonontus_ throughout México and Central America likewise are called _escorpiónes_. Although many people in various parts of Middle America consider most lizards poisonous, there is a unanimity of opinion concerning the venomous qualities of the various kinds of _escorpiónes_. I know of only two other lizards in Middle America that are so uniformly regarded in native beliefs; these are _Enyaliosaurus clarki_ in the Tepalcatepec Valley in Michoacán, called _nopiche_, and _Phrynosoma asio_ in western México, called _cameleón_.

=Sphaerodactylus lineolatus= Lichtenstein

15 km. NW of Chinajá, 1; Toocog, 1.

These small geckos were much more abundant than the few specimens indicate. They frequently were seen on the trunks of corozo palms, where they quickly took refuge in crevices at the bases of the fronds. The specimen obtained at Toocog was under the bark of a standing dead tree. In life the ventral surface of the tail was orange. The individual from Chinajá was in the leaf litter on the ground at the base of a dead tree.

=Thecadactylus rapicaudus= (Houttuyn)

15 km. NW of Chinajá, 1; 20 km. NNW of Chinajá, 2.

Two specimens were found beneath the bark of standing dead trees; another was found in the crack in the trunk of a mahogany tree about 13 meters above the ground. In life the dorsum was yellowish tan with dark brown markings; the venter was yellowish tan with brown flecks, and the iris was olive-tan. The largest specimen is a male having a snout-vent length of 95 mm.; all specimens have regenerated tails. Individuals when caught twisted their bodies and attempted to bite; upon grabbing a finger they held on with great tenacity.

=Anolis biporcatus= (Wiegmann)

14 km. NNW of Chinajá, 1; 17 km. NNW of Chinajá, 1; 20 km. NNW of Chinajá, 3; 30 km. NNW of Chinajá, 1; Sayaxché, 1.

All specimens of this large anole were obtained from trees. Some individuals were found in the tops of trees immediately after they were felled. My limited observations on this anole suggest that it is an inhabitant of the upper levels of the forest. In life an adult male from 20 kilometers north-northwest of Chinajá was brilliant green above; the eyelids were bright yellow; the belly was white. The outer part of the dewlap was pale orange, and the median part was pinkish blue. A juvenile having a snout-vent length of 47 mm. and a tail length of 86 mm. was pale grayish green with pale gray flecks on the dorsum. The largest male has a snout-vent length of 98 mm. and a tail length of 217 mm.; the same measurements of the largest female are 89 and 213 mm. This species, together with all other anoles, is known locally as _toloque_.

=Anolis capito= Peters

Chinajá, 2; 14 km. NNW of Chinajá, 1; Río de la Pasión, 1.

All individuals were observed on trunks of trees between heights of three and ten meters above the ground. The largest male has a snout-vent length of 81 mm. and a tail length of 155 mm.; the same measurements of the largest female are 87 and 150 mm. The streaked brown dorsum, combined with the lizards' habit of pressing the body against the trunks of trees, make this anole especially difficult to see.

=Anolis humilis uniformis= Cope

Chinajá, 24; 15 km. NW of Chinajá, 22; 20 km. NNW of Chinajá, 6; Sayaxché, 1.

This small dull brown anole is a characteristic inhabitant of the forest floor, where the lizards move about in a series of quick, short hops and thus easily evade capture. Three individuals were found on small bushes, and four were on the bases of trees; otherwise, all were observed on the ground. Observations indicate that this species is active throughout the day, except during and immediately after heavy rains. The males have a deep red dewlap with a dark blue median spot.

=Anolis lemurinus bourgeaei= Bocourt

Chinajá, 11; 20 km. NNW of Chinajá, 4; 30 km. NNW of Chinajá, 2; Río de la Pasión, 1; Río San Román, 1; Sayaxché, 8; Toocog, 6.

This moderate-sized anole characteristically inhabits the low bushes and bases of trees in the forest. Individuals were most readily observed on the buttresses of some of the gigantic mahogany and ceiba trees. When approached the lizards usually ran around the tree or ducked to the other side of the buttress; if the observer moved closer, they jumped to the ground and ran off. None was observed to ascend large trees. Some individuals were observed foraging on the forest floor; these took shelter on the bases of trees. One individual was sleeping on a palm frond at night. The adult males have a uniformly orange-red dewlap.

=Anolis limifrons rodriguezi= Bocourt

15 km. NW of Chinajá, 2; 20 km. NNW of Chinajá, 1.

In dry forests and more open situations than occur at Chinajá this little anole is abundant, but in the wet forests of southern El Petén, only three specimens were found. Two were on palm fronds about two meters above the ground; the other was on a low bush. I suspect that ecologically this species overlaps _A. humilis uniformis_ and _A. lemurinus bourgeaei_, but too few observations are recorded to justify a definite statement at this time.

=Anolis sericeus sericeus= Hallowell

Chinajá, 2; Sayaxché, 1; Toocog, 1.

This small anole is common and widespread in the Atlantic lowlands of southern México and northern Central America; usually it inhabits sub-humid regions. Consequently, its presence in the wet forests of southern El Petén was unexpected. The specimens from Chinajá were sleeping on low bushes at night, whereas the others were found on bushes by day.

=Basiliscus vittatus= Wiegmann

Chinajá, 6; Río de la Pasión, 1; Río San Román, 1; Sayaxché, 3; Toocog, 1.

Individuals of this abundant species were most frequently seen in dense bushes along the margins of rivers or small streams. None was observed far from water. These lizards, like the anoles, are known locally as _toloque_.

=Corythophanes cristatus= (Merrem)

Chinajá, 3; 20 km. NNW of Chinajá, 1.

Three individuals were found on tree trunks; the fourth was on a thick vine about one meter above the ground. The two largest males have snout-vent lengths of 121 and 115 mm. and tail lengths of 265 and 243