In many species of _Bufo_ the crown of the head forms more or less prominent ridges, especially strong in the region between the eyes; for instance, in _B. melanostictus_ and _B. lentiginosus_. The skin overlying these ridges is liable to be involved in the cranial ossification, and this reaches its greatest extent in the two Cuban species _B. empusus_ and _B. peltocephalus_. It is a curious coincidence, to say the least, that such dermal ossifications should be best developed in Neotropical species, in those very countries which amongst the Cystignathidae have produced the abnormal genera _Triprion_, _Calyptocephalus_, and _Pternohyla_. The most peculiar and odd-looking species is _Bufo ceratophrys_, a native of Ecuador, which has the upper eyelid produced into a horn-like appendage, the two sharply-pointed cones standing out transversely, reminding us of several species of the Cystignathoid genus _Ceratophrys_; there is also a series of four small pointed {180}appendages on each side of the body. Protective concealment is possibly the reason of these queer outgrowths. _B. viridis_ s. _variabilis_, the Green or Variable Toad, reaches a length of about 3 inches, and is the prettiest toad of Europe. The skin is distinctly smooth, the numerous porous, large and small warts being flattened. Parotoid glands are well developed, and a similar pair of glands sometimes occurs on the inner side of the calf, especially in Central Asiatic and in Algerian specimens. The coloration is very variable and changeable. The ground-colour of the upper parts is creamy, with large and small, partly confluent and irregularly shaped spots and patches of green, here and there interspersed with vermilion-red specks, especially along the sides of the back. The under parts are whitish, sometimes spotted with black. The iris is brass-coloured, greenish-yellow, with fine dark dots. The male does not differ from the female in size, but has an internal subgular vocal sac, a conspicuous callosity on the inner side of the first finger, and nuptial brushes on the first three fingers and on the inner palmar tubercle. The changing of colour affects mainly the intensity of the green; the same individual which now looks almost uniformly dull, almost grey, with dusky olive patches, will, if put into grass and sprinkled with water, within a few minutes appear in a tastefully combined garb of grass-green on a creamy ground. Some Southern and Eastern specimens have a creamy stripe along the vertebral line, thereby closely resembling _B. calamita_, from which, however, they can always be distinguished by the little pads below the joints of the toes; these pads being single in B. viridis, and double in _B. calamita_ and in _B. vulgaris_.