b. Neotropical. Metasternum small, cartilaginous or membranous. With discs.
1. With a pair of dermal scales on the discs. Omosternum with a bony style.
Tongue heart-shaped. Ecuador, 2 species .......... Hylixalus.
Toes free. 5 species .......... Phyllobates, p. [242].
Tongue entire. Ecuador and Colombia, 3 species .......... Prostherapis.
Omosternum cartilaginous. Ecuador .......... Phyllodromus pulchellus.
2. Discs without scales. Omosternum absent. Colombia .......... Colosthetus latinasus.
Phyllobates.[[105]]–This is one of the few Neotropical genera, and like nearly all of these has peculiar adhesive discs on the fingers and toes, each disc bearing on its upper surface two dermal scales. The tympanum is distinct. Vomerine teeth are absent. The general appearance of the five species is that of tree-frogs. One species, Ph. bicolor, yellowish above, dark brown beneath, lives in Cuba. The others inhabit Central America and Venezuela. They seem to have peculiar nursing habits. Ph. trinitatis of Venezuela and Trinidad carries its tadpoles on its back, on to which the young fix themselves by means of their suckers. Nothing is known about their breeding habits, for instance whether the young are hatched on the back, or, as seems more likely, if the parents (the specimen described by Boulenger[[106]] is a male) only give their offspring a temporary lift in order to convey them from a drying-up pool to a healthier place. It is remarkable that several species of Dendrobatinae, which inhabit the same countries, have precisely the same habits.[[107]]
Arthroleptis.–Slender and long-limbed little frogs, about one inch in length. The fingers and toes are free, very slender, and end in slightly dilated tips, the supporting phalanges being simple. The tympanum is variable. The skin is smooth or finely granulated. The colours are inconspicuous, brown or grey tones usually prevailing. About ten species are known, mostly from Continental Africa, a few from Madagascar and the islands in the Indian Ocean.
A. seychellensis.–Brauer[[108]] has discovered the mode of nursing of this frog. He found a specimen of A. seychellensis which carried nine tadpoles on its back, in the month of August, in the Seychelles, about 1500 feet above sea-level, upon an old tree-fern. The little ones were already provided with long tails, the hind-limbs were partly free, the fore-limbs still covered by the skin, and they held on by their bellies; not, like the young of Phyllobates, by their "suckers." Another specimen carried young which were still further developed. He also found an old frog, near which was lying a little heap of eggs, not enveloped in a common mass of jelly. The old frog escaped, but the eggs were taken care of in a vessel with moist sand at the bottom. By the following morning the eggs were hatched and the tadpoles were clinging by their bellies on to the walls of the glass. Brauer concludes that the young, when hatched, creep on to the parent's back, he or she waiting near the heap of eggs until the latter are ready. Curiously enough, he did not find out the sex of the nurse, nor are we told if the young are taken to the nearest water to finish their metamorphosis, or if they remain upon the parent's back until they hop off as baby-frogs. The yolk is very large. When the four limbs are already developed, the gill-cavity possesses no gills and no outer opening; and since the lungs are only just beginning to sprout, the tadpole must needs breathe by means of its skin. The jaws have no horny coverings. The adults live on the ground between moist leaves, and eat chiefly termites.