Data that are used to arrive at a systematic arrangement of the species of _Ptychohyla_ are analyzed and discussed below for the values inherent in the analysis. These data are of some value also in the recognition of species and subspecies but if employed for that purpose the data must be used in combination with the keys and the diagnoses of the individual species and subspecies. External Morphology Each of the external morphological characters used in the systematic treatment of _Ptychohyla_, as well as the nature of the tongue, is discussed below. SIZE AND PROPORTIONS.--Comparisons of size and certain proportions are given in Table 1. Frogs of this genus are small; the largest specimen examined is a female of _P. euthysanota euthysanota_ having a snout-vent length of 53.3 mm. The species comprising the _Ptychohyla schmidtorum_ group are smaller; the largest specimen examined is a female of _P. schmidtorum schmidtorum_ having a snout-vent length of 38.0 mm. An analysis of the various measurements and proportions shows few constant differences. _Ptychohyla ignicolor_ differs from all of the other species in having the head slightly wider than long and the tympanum noticeably less than half the size of eye. _Ptychohyla spinipollex_ has a relatively narrow interorbital distance, approximately equal to the width of the eyelid, whereas in all of the other species that distance is much more than the width of the eyelid. SNOUT.--All species have a blunt snout. In _P. leonhardschultzei_ and _P. ignicolor_ the snout is nearly square in lateral profile; in _P. schmidtorum_ the snout is slightly rounded above and below, and in the other species it is rounded above. _Ptychohyla leonhardschultzei_ and _P. spinipollex_ have a vertical fleshy rostral keel on the snout; in these species, because of this keel, the snout in dorsal profile is pointed. The nostrils are slightly protuberant in all species, and in _P. schmidtorum_ the internarial region is slightly depressed.