_Ptychohyla euthysanota_ and _P. schmidtorum_ have white stripes on the upper lips and on the flanks. All species have some form of a pale stripe above the anus and usually rather distinct white or pale stripes along the ventrolateral edges of the tarsi and forearms. There are no bright or boldly marked flash-colors (colors that are revealed only when the hind limbs are extended), except in _P. ignicolor_, which has bright red flash-colors in the groin and on the thighs. In life the iris varies from several different shades of bronze color to deep red in _P. schmidtorum schmidtorum_. The degree of metachrosis is moderate. Usually any change of color in life consists only of change in the intensity of color. At times when the over-all coloration is darkened some markings are obscured. Osteology The following description of the skull, hyoid, sternum, and prepollex is based on a male specimen of _P. spinipollex_ (KU 68632) that has been cleared and stained. The broad, flat skull (Fig. 3) has a large frontoparietal fontanelle. The ethmoid is large and has a flange laterally. The nasals are of moderate size and in broad contact with the ethmoid, but are separated from one another medially. The anterior half of the maxillary bears a thin, high flange. The anterior process of the squamosal is short and widely separated from the maxillary. The quadratojugal is a small spine-shaped element projecting anteriorly from the ventral base of the quadrate; the quadratojugal does not articulate with the maxillary. [Illustration: FIG. 3. Dorsal aspect of skull of _Ptychohyla spinipollex_ (KU 68632). Arrow indicates reduced quadratojugal.] The posteromedian part of the hyoid plate is calcified; from this plate the long bony, posterior cornua (thyrohyales) extend posterolaterally. The omosternum is calcified, widest anteriorly, and has a convex anterior edge. The calcified xiphisternum is roughly bell-shaped having short lateral processes anteriorly and a deep notch posteriorly. The swollen thumb is supported by a dorsoventrally flattened spine that does not extrude through the skin. VARIATION.--In general, the skull varies little. Usually the quadratojugal is present only as a short element attached to the quadrate, but in one specimen of _P. spinipollex_ the quadratojugal articulates with the maxillary and forms a complete quadratojugal-maxillary arch on each side of the skull. One specimen of _P. leonhardschultzei_ has a complete arch on one side and an incomplete arch on the other. Only _P. spinipollex_ has lateral processes anteriorly on the xiphisternum; in the other species the xiphisternum is deeply bell-shaped.