[Illustration: FIG. 1. Species of _Osteocephalus_: Top. _O. pearsoni_, KU 136312, [M]; Middle. _O. buckleyi_, KU 123172, [M]; Bottom. _O. verrucigerus_, KU 123177, [M]. x1.5.] [Illustration: FIG. 2. Species of _Osteocephalus_: Top. _O. leprieurii_, KU 126611, [F]; Bottom. _O. taurinus_, KU 126648, [M]. x1.] [Illustration: FIG. 3. Diagrammatic views of ventral color patterns in _Osteocephalus_: a. _O. pearsoni_, UMMZ 57533, [M]; b. _O. taurinus_, USNM 166037, [M]; c. _O. verrucigerus_, KU 123185, [F].] _Skin._--The dorsal skin of all males of _Osteocephalus_ is tuberculate to varying degrees, whereas the dorsal skin of females is smooth, or nearly so (Fig. 4). _Osteocephalus verrucigerus_ differs from other members of the genus by the presence of numerous, large tubercles bearing keratinized tips. The tubercles of _leprieurii_ are numerous and spinous but much smaller than those of _verrucigerus_; those of _taurinus_ are spinous but less numerous than in _leprieurii_. _Osteocephalus buckleyi_ has a mixture of large and small, non-spinous tubercles, and _pearsoni_ has only a few, small, scattered, non-spinous tubercles. Fleshy tubercles occur on the eyelids and supratympanic fold in females of _buckleyi_; a few small tubercles are present on the back of females of _pearsoni_, whereas the dorsal skin in females of the other species is smooth. The skin on the flanks of both sexes of _buckleyi_ is weakly areolate; in the other species the flanks are smooth. The skin on the top of the head in _taurinus_ is rugose as a consequence of co-ossification. In all species the anal opening is directed posteriorly at the upper level of the thighs.