were furnished by the late Luis Macías Arellano of the Dirección General de Caza. Each of these individuals has my profound thanks for his indispensable aid.

Field work on hylid frogs in Middle America has been supported by the National Science Foundation, Grant NSF-G9827, and this is the 9th publication on the results of study of the material from America.

During the course of this study I have examined 247 frogs that I assign to the genus Ptychohyla, plus 40 lots of tadpoles and 12 skeletal preparations. Furthermore, I have examined all of the type specimens. I have studied each of the species and subspecies in the field and have examined from seven (P. euthysanota macrotympanum) to 33 (P. spinipollex) living individuals of each species.

Measurements given in the analysis of data and in the descriptions of the species are those described by Duellman (1956). In the descriptions of living colors the capitalized names are from Ridgway (1912). All interpretations of osteological characters are based on specimens cleared in potassium hydroxide and stained with alizarin red.

Recordings of the breeding calls were made with a Magnemite Portable Tape-recorder; audiospectrographs were made on a vibralyzer (Kay Electric Company) using normal pattern and wide bandwidth.

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.

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.