_Remarks._--Cope (1887:12) described _Scytopis boulengeri_ from Nicaragua. Günther (1901:267) placed _boulengeri_ in the genus _Hyla_, and stated that Cope possibly placed _boulengeri_ in the genus _Scytopis_ on the supposition that it had an accumulation of "sebaceous glands" above the tympanum. Noble (1918:339) redescribed _Hyla boulengeri_ on the basis of three specimens from Zelaya Province, Nicaragua, and noted that the glands were not prominent in any of the specimens. Duellman (1956:8) showed that _Scytopis hebes_ (generotype of _Scytopis_ by monotypy) is a Phrynohyas, and thus placed _Scytopis_ Cope, 1862, in the synonymy of _Phrynohyas_ Fitzinger, 1843. Dunn and Emlen (1932:25) placed _Hyla lancasteri_ Barbour in the synonymy of _Hyla boulengeri_; the former was known solely from one juvenile. They made no qualifying statements, but probably they were impressed by the strongly barred thighs, a coloration known among Central American hylids at that time only in _Hyla boulengeri_ (Duellman, 1966a:271). Taylor (1952:856) followed Dunn and Emlen with reservation and noted some differences. Duellman (1966a:271) showed that the holotype of _lancasteri_ was a juvenile of a species subsequently named as _Hyla moraviaensis_ by Taylor (1952:865). In Central America, _Hyla boulengeri_ can be confused only with _Hyla foliamorta;_ the latter is restricted to central and eastern Panamá and northern Colombia. The snout of _foliamorta_ is more pointed and protruding, and the vocal sac is darker than in _boulengeri_; the groin of _foliamorta_ usually is creamy white, whereas _boulengeri_ usually has a dark spot. The skulls differ in that _boulengeri_ has a frontoparietal fontanelle, the prevomer is larger and elongate, anteriorly connected to the premaxillary, and posteriorly separated from the sphenethmoid by cartilage; _foliamorta_ lacks a fontanelle, the prevomer is smaller, anteriorly separated from the premaxillary by cartilage, but connected by a bony suture to the sphenethmoid. The mating call of _boulengeri_ differs by having shorter notes, twice as many pulses per second, a higher fundamental frequency, and more closely approximated major frequencies than does that of _foliamorta_. _Hyla boulengeri_ need not be compared in detail with the other Central American members of the _Hyla rubra_ group, because all of them are smaller and have shorter snouts, smoother skin, and dissimilar color patterns. _Distribution._--In Central America _Hyla boulengeri_ inhabits the forested lowlands in locally humid areas in Guanacaste Province, Costa Rica, and in the humid Golfo Dulce region of Costa Rica; it occurs on the Carribbean lowlands from central Nicaragua to South America, where it ranges to Guyana and Ecuador. The highest elevations where _H. boulengeri_ has been found are 620 meters at Turrialba, Cartago Province, and 700 meters at Tilarán, Guanacaste Province, Costa Rica (Fig. 4).