_Ptychohyla schmidtorum_ and _P. ignicolor_ have slightly longer premaxillaries than the other species. The longer premaxillary is reflected in the larger number of teeth on the bone--9 to 11 (average 10) in four specimens of _P. schmidtorum_ and 10 teeth in one _P. ignicolor_, as compared with 6 to 10 (average 7.9) in seven specimens of the other species. The number of maxillary teeth in the various species are: _P. euthysanota euthysanota_, 43; _P. euthysanota macrotympanum_, 38; _P. leonhardschultzei_, 38 and 40; _P. spinipollex_, 34 and 40; _P. schmidtorum schmidtorum_, 37 and 43; _P. schmidtorum chamulae_, 40 and 41; _P. ignicolor_, 43. The teeth on the premaxillary and anterior part of the maxillary are long, pointed, and terminally curved backwards. Posteriorly on the maxillary the teeth become progressively shorter and blunter. Variation in number of vomerine teeth is shown in Table 1. [Illustration: FIG. 4. Tadpoles of the _Ptychohyla euthysanota_ group: (A) _P. euthysanota euthysanota_ (KU 60042), (B) _P. euthysanota macrotympanum_ (KU 60049), (C) _P. leonhardschultzei_ (KU 68556), and (D) _P. spinipollex_ (KU 60053).] Tadpoles Tadpoles of the genus _Ptychohyla_ are adapted to live in mountain streams. The bodies are streamlined, and the tails are long and have low fins (Figs. 4 and 5). The mouths are large and directed ventrally. Tadpoles of the two groups of species have strikingly different mouthparts. [Illustration: FIG. 5. Tadpoles of (A) _Ptychohyla schmidtorum schmidtorum_ (KU 60051), (B) _P. schmidtorum chamulae_ (KU 58199), and (C) _P. ignicolor_ (KU 71716).] Lips of tadpoles of the _Ptychohyla euthysanota_ group (Fig. 6 A-D) are folded laterally; there are 4/6 or sometimes 4/7 tooth-rows. A lateral "wing" projects on either side of the upper beak. The beaks have blunt, peglike serrations. Lips of tadpoles of the _Ptychohyla schmidtorum_ group (Fig. 6 E-G) are greatly expanded and form a funnel-shaped disc; there are 3/3 short tooth-rows. There is no lateral projection or "wing" on either side of the upper beak. The beaks have long, pointed serrations. [Illustration: FIG. 6. Mouthparts of tadpoles of _Ptychohyla_: (A) _P. euthysanota euthysanota_ (KU 60042), (B) _P. euthysanota macrotympanum_ (KU 60049), (C) _P. leonhardschultzei_ (KU 68556), (D) _P. spinipollex_ (KU 60053), (E) _P. schmidtorum schmidtorum_ (KU60051), (F) _P. schmidtorum chamulae_ (KU 58199), and (G) _P. ignicolor_ (KU 71716). x 10.] Variation in certain structural details and in coloration is discussed for each species and subspecies in the systematic accounts that follow. Sizes, proportions, and numbers of tooth-rows are tabulated in Table 2. TABLE 2.--COMPARISON OF CERTAIN LARVAL CHARACTERS IN THE SPECIES OF PTYCHOHYLA. (MEANS ARE IN PARENTHESES BELOW THE RANGES.)