_Hands and Feet._--The feet of _Osteocephalus_ are fully webbed or nearly so. Webbing between fingers one and two is basal in all species. Webbing between fingers two, three, and four is most extensive in _taurinus_, in which the three fingers are about one-half webbed (Fig. 5). _Osteocephalus buckleyi_, _pearsoni_, and _verrucigerus_ have reduced webbing between fingers two and three, and _leprieurii_ has reduced webbing between fingers two, three, and four. All members of the genus have well-developed subconical subarticular tubercles on the fingers and toes; there is a tendency for the distal tubercle on the fourth finger to be weakly bifid. Palmar and plantar supernumerary tubercles are well developed in _taurinus_, moderately developed in _buckleyi_, _leprieurii_, and _pearsoni_, and barely evident in _verrucigerus_. All of the species have a noticeable fold on the wrist and enlarged prepollices, bearing horny nuptial excrescences in breeding males. The prepollex is least enlarged in _buckleyi_. Outer metatarsal tubercles are absent. The inner metatarsal tubercle is moderately well developed and ovoid in _leprieurii_ and _pearsoni_; it is elliptical and flat in the other species. Tarsal folds are absent in all species except _verrucigerus_, in which the folds are barely evident. [Illustration: FIG. 4. Segments of dorsal skin of males of _Osteocephalus_ showing size and arrangement of tubercles: a. _O. verrucigerus_, KU 123183; b. _O. taurinus_, USNM 166033; c. _O. leprieurii_, KU 126616; d. _O. buckleyi_, USNM 165999. Each square = 1 sq. cm.] _Cranium._--As a genus, the cranial structure is remarkably uniform and quite generalized when viewed in the context of the family Hylidae. The skulls are broad and relatively flat, each being only slightly more broad than long and about one-third as high as long. In dorsal aspect the snouts are broadly rounded; the snout of _buckleyi_ is somewhat less rounded and appears to be slightly longer than the snouts of other species. This subtle difference relates to the relative narrowness of the premaxillaries in _buckleyi_. [Illustration: FIG. 5. Palmar views of hands of males of _Osteocephalus_: a. _O. buckleyi_, KU 109506; b. _O. leprieurii_, KU 126627; c. _O. pearsoni_, MCZ 15565; d. _O. taurinus_, KU 126653; e. _O. verrucigerus_, KU 123177. x4.] [Illustration: FIG. 6. Skulls of two species of _Osteocephalus_: a and b. _O. leprieurii_, KU 125961; c and d. _O. pearsoni_, UMMZ 67465. x3.]