It is extremely doubtful if the frog described and illustrated by Boulenger could be associated with either _Hyla phlebodes_ or _H. microcephala microcephala_. Individuals of the former species lack a dorsolateral white line and always have some dorsal markings evident at night; furthermore, _H. phlebodes_ is not known to occur on the Pacific lowlands. _Hyla microcephala microcephala_ occurs farther southeast. Since there is no reason to doubt the type locality of _H. underwoodi_, since specimens from the area around the type locality that have been preserved at night are like the holotype in pattern, and since the characteristics of the populations of the frogs in Guanacaste are the same as, or gradually blend into those of, populations in northern Central America and southern México, the frogs from throughout the entire range can be referred to one taxon, the earliest name for which is _Hyla underwoodi_ Boulenger, which herein is considered to be a subspecies of _H. microcephala_ Cope. _Distribution._--_Hyla microcephala underwoodi_ inhabits the Atlantic slopes and lowlands from southern Veracruz and extreme northern Oaxaca eastward across the base of the Yucatan Peninsula (possibly the species is extant in the northern part of the peninsula) to British Honduras and thence southeastward through the Caribbean lowlands and interior valleys in Honduras to central Nicaragua, where it apparently avoids the forested Caribbean lowlands and the dry Pacific lowlands of northwestern Nicaragua, but in the vicinity of Managua invades the Pacific lowlands and continues southward into northwestern Costa Rica as far as the Puntarenas Peninsula (Fig. 1). In México and Guatemala the species has not been taken at elevations of more than 350 meters, whereas farther south it occurs at higher elevations--780 meters at Silencio, Costa Rica, 830 meters on Montaña de Guaimaca, Honduras, 960 meters at Finca Tepeyac, Nicaragua, and 1200 meters at Finca Venecia, Nicaragua.