_Remarks._--This description brings to eight the number of species now recognized in the _Hyla bistincta_ group. _Hyla siopela_ is most closely related to _Hyla robertsorum_ from the high mountains of the Sierra Madre Oriental in northern Puebla and eastern Hidalgo. Possibly the four species now recognized in the _crassa_ subgroup (_crassa_, _pachyderma_, _robertsorum_, and _siopela_) are only subspecies of a single species, but differences in the amount of webbing in _crassa_ and the nature of the nuptial excrescenses in _pachyderma_ indicate that they are distinct species. The type locality of _Hyla siopela_ is a small stream cascading down the western slope of Cofre de Perote; the lower reaches of the stream can be reached by a dirt road leading east from the village of Perote for about 2 kilometers to a small park. The frogs were found in the stream at elevations of 50 to 100 meters higher than the park. The stream flows through a ravine supporting open, dry pine forest. Although the stream was searched thoroughly in February, 1966, no frogs were found. In July, 1966, adults and juveniles were found in crevices and under overhanging rocks behind small cascades and waterfalls by day and sitting on rocks and branches in the spray of cascades at night. The specific name _siopela_ is derived from the Greek _siopelos_, meaning silent, and alludes to the absence of a voice in this species. Hyla altipotens new species Plate 19 _Holotype._--Adult male, KU 101001, from 37 kilometers (by road) north of San Gabriel Mixtepec (kilometer post 183 on road from Oaxaca to Puerto Escondido), Oaxaca, Mexico, elevation 1860 meters; obtained on February 19, 1966, by William E. Duellman. _Paratypes._--KU 101002-6 collected at the same locality on February 19 and 20, 1966, by William E. Duellman, and KU 101008 from 33 kilometers (by road) north of San Gabriel Mixtepec, Oaxaca, Mexico, elevation 1675 meters; obtained on February 20, 1966, by Linda Trueb. _Diagnosis._--A member of the _Hyla taeniopus_ group characterized by a yellow venter, yellow flecks on posterior surfaces of thighs, bronze-colored stripe from snout, along canthus and edge of upper eyelid to point above arm, pointed snout, smooth dorsum, and no sexual dimorphism in shape of snout.