_Coloration._--All _Osteocephalus_ are predominantly brown frogs usually with some darker dorsal markings (Figs. 1 and 2). _Osteocephalus verrucigerus_ has a nearly uniform dark brown dorsum and no distinct transverse bars on the limbs, whereas all of the other species have distinct bars on the limbs. The dorsal markings on the body consist of irregular blotches in _buckleyi_, _pearsoni_, and _taurinus_ but are narrow transverse marks in _leprieurii_. A narrow middorsal cream or yellow stripe is present in some individuals of _buckleyi_ and _taurinus_ but absent in all individuals of the other species. The flanks are uniform pale tan in _leprieurii_ and uniform reddish brown in _verrucigerus_; in the other species the flanks are cream to brown with dark brown or black spots (also dark diagonal marks in some _buckleyi_). A creamy white anal stripe is present in some specimens of _leprieurii_ but absent in all individuals of other species. The postocular region, encompassing the tympanum, is dark brown in most specimens. In adults of _pearsoni_ and _taurinus_ the upper lips are dark brown. A pale cream or tan suborbital spot is present in _pearsoni_ and in some _taurinus_; in some specimens of _taurinus_ the suborbital spot is expanded posteriorly forming a labial stripe on the posterior part of the lip. The labial markings of _verrucigerus_ are similar to the latter pattern, except that in females a distinct, light labial stripe extends the length of the lip. _Osteocephalus leprieurii_ has a distinct, broad, pale labial stripe. The lips are barred cream and dark brown in _buckleyi_. The venter is uniform creamy white or pale tan in _leprieurii_, uniform white in some _buckleyi_ (most males), and uniform tan in some _taurinus_. The other species and some individuals of _taurinus_ and _buckleyi_ (most females) have dark ventral markings. These markings are most distinctive in _verrucigerus_, in which the venter is white with bold black mottling and spots (Fig. 3c). Those individuals of _taurinus_ having ventral markings usually have indistinct, diffuse brown spots on the throat and chest (Fig. 3b). _Osteocephalus pearsoni_ is characterized by a fine brown reticulation on the venter and on the anterior and posterior surfaces of the thighs in adults (Fig. 3a). Individuals of _buckleyi_ that have ventral markings vary between the patterns illustrated for _pearsoni_ and _taurinus_ (Figs. 3b and c). Ontogenetic change in coloration is slight or non-existent in _buckleyi_, _pearsoni_, and _taurinus_, except that juveniles lack ventral markings. A dark blotch on the back and distinct transverse bars on the limbs are evident in juveniles of _verrucigerus_; these markings are obscured in the adults. Juveniles of _leprieurii_ are olive-brown with yellow dorsolateral stripes; the transverse dark marks, characteristic of the adults, appear before the stripes are lost.