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
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.
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.
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
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_.
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.