Body brown above; tip of snout cream color; grayish cream color below; caudal musculature creamy tan; caudal fin transparent; cream-colored crescent-shaped mark on posterior edge of body and anterior part of caudal musculature, bordered posteriorly by dark brown blotch; scattered brown flecks on caudal musculature and posterior part of caudal fin. Eye bronze color in life. _Variation._--The variation in size and proportions is given in Table 2. In some specimens the first upper tooth-row is irregular, sometimes broken, and often shorter than other upper tooth-rows. Usually the fourth upper and first lower, and sometimes the sixth lower, tooth-rows are interrupted medially. One specimen has a short, irregular, seventh lower tooth-row; all others have six. The cream-colored crescent-shaped mark usually is distinct. The brown blotch posterior to this mark is variously shaped ranging from a narrow vertical bar to a triangular blotch. Brown flecks seldom are present on the anterior part of the ventral caudal fin. _Comparisons._--Aside from the characters given in the diagnosis, _P. euthysanota euthysanota_ can be distinguished from both _P. spinipollex_ and _P. leonhardschultzei_ by the absence of bold black and white marbling on the flanks; furthermore, from the former it can be distinguished by having more and smaller horny nuptial spines and from the latter by having the snout, in lateral profile, rounded above and not acutely angulate. _Ptychohyla euthysanota euthysanota_ differs from _P. euthysanota macrotympanum_ by normally having a darker dorsal color, broader stripe on upper lip, and a distinct lateral stripe. Occurring sympatrically with _Ptychohyla euthysanota euthysanota_ are several species of _Plectrohyla_, all of which differ in having a bony prepollex, rather rugose skin on the dorsum, and more squat bodies. Other sympatric species are _Ptychohyla schmidtorum schmidtorum_, which lacks a tarsal fold and nuptial spines and has a red eye in life, _Hyla salvadorensis_, which has a green dorsum and lacks spinous nuptial tuberosities, and _Hyla sumichrasti_, a small yellow frog usually lacking vomerine teeth. _Life History._--This subspecies breeds in clear, swift mountain streams. Males call from stems and leaves of plants at the edge of, or overhanging, the streams. The breeding call consists of a soft "wraack," repeated at intervals of three to four seconds. Each note has a duration of 0.60 to 0.65 seconds and has 91 to 102 pulses per second; the dominant frequency falls between 3000 and 3200 cycles per second.