The parasphenoid is the first of the palatal bones to appear. At metamorphosis the bone is well developed; the anterior tip is situated just in front of the anterior edge of the orbit, and posteriorly the lateral processes extend laterally beyond the ossified parts of the auditory region. The pterygoids do not appear until metamorphosis, when ossification is evident in only the mid-parts of the posterolateral arms. Ossification follows in the mid-parts of the anterolateral arms and occurs last in the pterygoid pedicles. The palatines do not appear until all three arms of the pterygoids are at least partly ossified. Ossification proceeds rapidly from the maxillaries medially to the unossified ethmoid, which is the last of the cranial bones to appear. Initially it is extremely shallow; dorsally it is widely separated from the nasals, and ventrally the posterior margin meets the anterior point of the parasphenoid. In dorsal view, ossification proceeds anteriorly between the nasals and posteriorly, ventral to the frontoparietals; ventrally, ossification proceeds posteriorly dorsal to the parasphenoid. The ventral arms of the squamosal and the supraoccipital region of the exoccipital are the first occipital bones to appear. Ossification follows in the regions of the semicircular canals and occipital condyles. The dorsal end of the ventral arm of the squamosal and the posterior arm of the squamosal ossify as a unit at the same time the quadratojugal appears. Shortly thereafter the anterior arm of the squamosal ossifies, the distal part of the columella appears, and the anterior and lateral parts of the auditory region ossify. The angular and dentary of the lower jaw appear concurrently with the dentigerous bones. Initially, the angular is short and broad; the articular surface is absent, and the anterior end is slightly overlapped by the dentary. The mentomecklians do not ossify until approximately the same time that the quadratojugal appears in the upper jaw. _Comparative Osteology_ The genus _Smilisca_ is characterized by the following combination of cranial osteological characters: (1) A large amount of bone is involved in the skull and a minimal amount of cartilage and/or secondarily ossified cartilage; co-ossification is absent. (2) The skulls are uniformly broad with angular lateral margins, and truncate anteriorly. (3) An internasal septum and quadratojugals are present. (4) A well-developed squamosal minimally extends one-fourth the distance from the dorsal end of the quadrate to the maxillary, and maximally is separated from the maxillary by a suture. (5) The ethmoid is large; the distance between the anterior end of the ethmoid and the anterior edge of the premaxillary varies between 15 and 20 per cent of the total length of the skull.