The growth and development of the other species of _Smilisca_ do not differ significantly from that of _S. phaeota_. The tadpoles of _S. sila_ and _sordida_ from streams have relatively longer tails at hatching. For example, in tadpoles of _S. sordida_ the average length of tail is 64.0 per cent of the body-length in stage 25, and in stage 37, 67.0 per cent. _Behavior_ The tadpoles of _S. baudini_, _cyanosticta_, _phaeota_, and _puma_ are pelagic inhabitants of shallow ponds. Early stages of _S. baudini_ in which external gills are present have been observed to hang vertically with the gills spread out at the surface of the water, a behavior noted by Zweifel (1964:206) in tadpoles of _Phrynohyas venulosa_, which also develop in warm, standing water having a relatively low oxygen-tension. When disturbed the pelagic tadpoles usually dive and seek shelter amidst vegetation or in mud on the bottom. This behavior was observed in _S. baudini_, _cyanosticta_, and _phaeota_ by day and at night. No tadpoles of _S. puma_ were observed by day; those seen at night were near the surface of small water-filled depressions in a grassy marsh; they responded to light by taking refuge in the dense grass. Perhaps tadpoles of this species are negatively phototactic and remain hidden by day. The stream-inhabiting tadpoles of _S. sila_ and _sordida_ live in clear pools in rocky streams, where they were observed to cling by their mouths to rocks in the stream and to seek shelter amidst pebbles or beneath rocks and leaves on the bottom. These tadpoles are not found in shallow riffles. We have not found tadpoles of two species of _Smilisca_ in the same body of water and therefore cannot offer observations on ecological relationships in sympatric situations. PHYLOGENETIC RELATIONSHIPS Identifiable hylid remains are known from the Miocene to the Recent, but these fossils are mostly fragmentary and provide little useful information regarding the phylogenetic relationships of living genera. Frogs of the genus _Smilisca_ are generalized and show no striking adaptations, either in their structure or in their modes of life history. Interspecific Relationships In attempting to understand the relationships of the species of _Smilisca_ we have emphasized osteological characters. The phylogeny suggested by these characters is supported by other lines of evidence, including external morphology, tadpoles, and breeding calls.