_Description._--The following description is based on KU 57651 from El Chico Parque Nacional, Hidalgo. Adult male having a snout-vent length of 45.1 mm.; tibia length, 22.1 mm., 49.0 per cent of snout-vent length; foot length (measured from proximal edge of inner metatarsal tubercle to tip of longest toe), 21.5 mm.; greatest width of head, 13.7 mm., 30.4 per cent of snout-vent length; head length, 12.6 mm., 27.9 per cent of snout-vent length; diameter of eye, 4.0 mm.; diameter of tympanum, 1.8 mm., 45 per cent of diameter of eye. Snout short, in lateral profile blunt, in dorsal profile round; canthus rounded; loreal region slightly concave; lips thick, round, and not flaring; nostrils slightly protuberant; internarial distance, 3.6 mm.; interorbital distance, 4.0 mm., slightly broader than width of eyelid, 3.5 mm. A moderately heavy dermal fold from posterior corner of eye above tympanum and curving downward towards insertion of forearm; tympanum nearly round, covered by dermal fold above, its diameter slightly less than its distance from eye. Forearm moderately robust; distinct fold on wrist; prepollex much enlarged with patch of small nuptial spines continuous on side of digit; similar line of nuptial spines on inner edge of second finger; subarticular tubercles round, moderate in size, none bifid; supernumerary tubercles small and present only proximally; fingers long and slender; length of fingers from shortest to longest, 1-2-4-3; discs moderately large, that on third finger about size of tympanum; no web between first and second fingers; rudimentary web between other fingers. Legs robust; heels over-lap by about one-fourth length of shank when hind limbs adpressed; tibiotarsal articulation extending to posterior corner of eye; tarsal fold weak, extending to about middle of tarsus; inner metatarsal tubercle moderately large, flat, and elliptical; outer metatarsal tubercle small, round, and indistinct; subarticular tubercles round; supernumerary tubercles small, in single row on proximal segments of each digit; toes moderately long and slender; length of toes from shortest to longest, 1-2-5-3-4, the fifth nearly as long as third; toes nearly fully webbed; web extending to base of penultimate phalanx of fourth toe and to discs on other toes; discs small, about two-thirds size of those on fingers. Anal opening above middle of thighs; anal sheath short, deeply creased medially; heavy transverse dermal fold above anus; no large anal tubercles. Skin of all dorsal surfaces, chin, and ventral surfaces of limbs, except proximal parts of thighs, smooth; belly and proximal parts of thighs areolate; thoracic fold present, weak. Tongue elliptical, slightly longer than wide, not notched behind, and free posteriorly for about one-fourth of its length; vomerine teeth 3-3, situated on small, widely separated, transverse ridges between rather small elliptical inner nares; no vocal slits.