The head of the frog, Leiopelma hamiltoni McCulloch

S ummary. The cranial anatomy of the rare Stephens Island frog, Leiopelma hamiltoni , is compared with that of the other two species, L. hochstetteri and L. archeyi . For the most part it agrees closely with the detailed description previously given for these latter species. Although L. hamiltoni and L. archeyi exhibit considerable similarity in external appearance and live under more or less comparable habitat conditions, they show certain internal differences in head anatomy. Of eight characters known to be constant specific differences between L. archeyi and L. hochstetteri, L. hamiltoni agrees with L. archeyi in five and with L. hochstetteri in three.