Only the descriptions of the new species are given in this paper; detailed comparisons, descriptions of osteological features, analyses of calls, and discussions of relationships are reserved for a forthcoming review of the entire genus. In the spring of 1959, collections of amphibians and reptiles were made in the cloud forests on the northern slopes of the Sierra Madre Oriental in northern Oaxaca. Among the hylids found, two specimens of a heretofore unnamed species of _Ptychohyla_ have brilliant red flash-colors on the groin and thighs; in allusion to these fiery colors I propose that this species be named: ~_Ptychohyla ignicolor_~ new species (Plate 25, Fig. 1) _Holotype._--University of Michigan Museum of Zoology No. 119603, from a stream 6 kilometers south of Vista Hermosa, Oaxaca, México (1865 meters); obtained on March 31, 1959, by Thomas E. Moore. Original Number WED 14159. _Paratype._--UMMZ 119602 from Vista Hermosa, Oaxaca (1500 meters); obtained on March 30, 1959, by William E. Duellman. _Diagnosis._--A species of the _schmidtorum_-group of _Ptychohyla_ differing from other known members of the group in having the diameter of the tympanum less than one-half the diameter of the eye, no white spot below the eye, no lateral light stripe, bright green dorsum in life and red flash-colors on groin and thighs. _Description of Holotype._--Adult male having a snout-vent length of 30.0 mm.; tibia length, 14.6 mm.; tibia length/snout-vent length, 48.7 per cent; foot length (measured from proximal edge of inner metatarsal tubercle to tip of longest toe), 12.3 mm.; head length, 9.2 mm.; head length/snout-vent length, 32.3 per cent; head width, 9.3 mm.; head width/snout-vent length, 31.0 per cent; diameter of eye, 3.2 mm.; diameter of tympanum, 1.3 mm.; tympanum/eye, 40.6 per cent. Snout in lateral profile square, in dorsal profile obtusely rounded; canthus pronounced; loreal region slightly concave; lips moderately flaring; top of head flat; nostrils protuberant; internarial distance, 2.8 mm.; interorbital distance, 3.3 mm., much broader than width of eyelid, 2.8 mm. A heavy dermal fold from posterior corner of eye above tympanum to insertion of forelimb, covering upper edge of tympanum; tympanum elliptical, its greatest diameter equal to its distance from eye. Forearm robust with a distinct fold on wrist; pollex moderately enlarged without nuptial spines; second and fourth fingers equal in length; subarticular tubercles round; none is bifid; disc of third finger slightly larger than tympanum; no web between first and second fingers; vestige of web between other fingers. Heels overlap when hind limbs adpressed; tibiotarsal articulation extends to anterior corner of eye; no tarsal fold; inner metatarsal