_Diagnosis._--Size small ([M] 38.0 mm., [F] 46.0 mm.), differing from other species in the genus by the following combination of characters: skull about as long as broad; frontoparietal fontanelle keyhole-shaped; supraorbital flanges absent; squamosal small, not in contact with maxillary; bony portion of ethmoid terminating at anterior edge of orbit; tarsal fold weak, two-thirds length of tarsus; inner metatarsal tubercle small, low, flat, elliptical; snout rounded in dorsal profile; lips thin and flaring; fingers having only vestige of web; toes one-half webbed; diameter of tympanum about two-thirds that of eye; narrow labial stripe white; pair of dark brown (sometimes interconnected) stripes on tan dorsum; no blue spots on flanks or thighs; vocal sac in breeding males pale brown. (Foregoing combination of characters distinguishing _S. puma_ from other species in genus.) _Description and variation._--Ten breeding males from the vicinity of Puerto Viejo, Heredia Province, Costa Rica, have snout-vent lengths of 32.5 to 37.9 mm. (34.8 mm.). In these specimens, the length of the tibia to the snout-vent length is 0.48 to 0.53 (0.51), and the tympanum/eye ratio is 0.52 to 0.72 (0.65). Seven females have snout-vent lengths of 40.8 to 45.8 mm. (43.9 mm.). No individual has more than a vestige of a web between the second and third and fourth fingers. None has a web between the first and second fingers. Breeding males lack nuptial excrescences on the thumbs. The vocal sac is moderately large and bilobed.