The tympanic disc is very variable, large, small or quite hidden. Vomerine teeth are present or absent. The pupil contracts into a horizontal slit except in some Palaeotropical genera. The tongue is universally free behind, mostly deeply notched, and can be well protruded; only in the Indian _Oxyglossus_ and in the Neotropical genera, excepting _Hylixalus_, its posterior margin is entire.–There are terrestrial, arboreal, and aquatic members in this large sub-family. The geographical distribution of the Raninae, which comprise about twenty genera with at least some 270 species, is almost entirely Arctogaean. None, with the exception of three species in the Papuan subregion, occur in the Australian region; and only four genera, with one or two species each, inhabit the tropical Andesian district, the {240}remainder of South America being without any Raninae. All the species of the whole Periarctic region belong to the genus _Rana_ except in Eastern Asia, where the closely allied genus _Rhacophorus_ occurs also. The entire sub-family of Raninae is, in its fulness and diversity of development, essentially Palaeotropical. Many of the genera, even in the present more liberal sense as interpreted by Boulenger, are based upon unimportant characters, and in reality run into each other. This is for instance the case with _Rana_ and _Rhacophorus_. The following tabular arrangement is merely a key for determination and does not necessarily express relationships. The presence or absence of vomerine teeth is a character easily ascertained, but it separates closely allied genera, for instance, _Rhacophorus_ from _Ixalus_ and _Micrixalus_ from Rana. The genera with extra, interpolated phalanges are marked *. KEY FOR THE DETERMINATION OF THE GENERA OF RANINAE. I. Pupil vertical. _A_. With vomerine teeth. _a_. Omosternum very slender and cartilaginous. Small discs. India and Ceylon, 3 species .......... _Nannobatrachus._ _b_. Omosternum with a bony style. α. Outer metatarsals webbed. Small discs. South India, 2 species .......... _Nyctibatrachus._ β. Outer metatarsals close together. Africa. Fingers and toes with interpolated phalanges. Without terminal discs. 2 species .......... _Cassina._* With discs supported by claw-shaped phalanges, 10 species .......... _Hylambates._* Fingers and toes without interpolated phalanges; without discs. Toes webbed .......... _Trichobatrachus robustus_, p. 271. Toes free, with sharp claws .......... _Gampsosteonyx batesi_, p. 272. _B_. Without vomerine teeth. Discs well developed. Outer metatarsals united. Tropical Africa and Madagascar, 7 species .......... _Megalixalus._* {241}II. Pupil horizontal. _A_. With vomerine teeth. _a_. Outer metatarsals webbed together.