_H. aurea_ is one of the commonest and most beautiful species, occurring throughout Australia and Tasmania, excepting of course in the large deserts. It has the appearance and restlessness of a water-frog, is not unlike _Rana esculenta_, and grows to about three inches in length. The tympanum is very distinct, but rather small. The fingers are without a pollex-rudiment, the tarsus has a fold along its inner edge. The adhesive discs are decidedly small. The male has two internal vocal sacs, which bulge out sideways. The skin is smooth and shiny. The under parts are white; the upper parts are, speaking generally, a mixture of blue and olive, with blue or brown spots, but spirit-specimens give no idea of the beauty which this changeable species can assume. Sometimes the same individual is saturated blue and green, with several longitudinal stripes of burnished copper along the back; a few minutes later the stripes glitter {202}like gold, and in other moods the whole upper surface is mottled blue, green, and brown. My specimens often went into the water and did not climb. The food is said to consist chiefly of other small frogs in preference to insects. _Nototrema_ differs from _Hyla_ in so far as the female has a pouch on the back for the reception of the eggs. This bag is formed by an infolding of the skin; it opens backwards in front of the vent, it has a sphincter and is permanent, although it distends to larger dimensions when in use. An initial stage of such a pouch is possessed by _Hyla goeldii_ (Fig. 38). The pupil is horizontal, the tongue can be protruded but little; the tympanum is free, and the adhesive discs of the fingers and toes are well developed. These "marsupial frogs," of which about half-a-dozen species are known, live chiefly in the tropical forest-region of South America, notably from Peru to Venezuela. _N. marsupiatum_ is green with darker blue-green spots, or with longitudinal patches which are each surrounded by a whitish or yellow seam of little dots. The limbs have cross-bars. Total length about 2½ to 3 inches. The eggs of this species are comparatively small and numerous. The very small tadpoles have no external gills, and escape from the pouch to finish their metamorphosis in the water. _N. testudineum_, about 3 inches in length, is of a uniform lead-colour, but is lighter beneath. The skin of the back is studded with stellate calcareous deposits, a peculiarity which is alluded to in the specific name.