Along two cascading mountain streams in cloud forest on the northern slopes of the Mesa Central in central Chiapas numerous specimens of a distinctive species of _Ptychohyla_ were found in association with two species of _Hyla_ and two of _Plectrohyla_. The first specimen of this new species of _Ptychohyla_ was discovered by Dale L. Hoyt, who found the frog on a rock at midday. At night on August 5, 1960, numerous individuals were found calling from leaves of plants growing on the slopes of the ravine by the streams. None was more than two meters above the ground. Tadpoles were found in the fast-flowing stream, where they were holding onto rocks with their mouths. Little is known of the herpetofauna of these mountains that are the home of the Chamula Indians. Since the little frog described here comes from the land of the Chamulas, I propose that it be named: ~_Ptychohyla chamulae_~ new species (Plate 25, Fig. 2) _Holotype._--University of Kansas Museum of Natural History No. 58063, from a stream above (6.2 kilometers by road south) Rayón Mescalapa, Chiapas, México (1690 meters); one of a series collected on August 5, 1960, by William E. Duellman, Dale L. Hoyt, and John Wellman. Original No. WED 17327. _Paratypes._--KU Nos. 58064-58073 collected with the holotype. _Diagnosis._--A species of the _schmidtorum_-group of _Ptychohyla_ differing from other known members of the group in having the following combination of characters: diameter of tympanum not noticeably less than half that of eye; white spot below eye; white lateral stripe on body anteriorly; dorsum bright green in life; thighs yellowish brown.