The Toucans (a word derived from their Brazilian name, _Taca, Tucà_) received from Linnæus the title of _Ramphastos_, in allusion to the great volume of the beak ([Greek: ramphos]--Ramphos), a family (_Ramphastidæ_). In some respects, indeed, they resemble the Hornbills in the development of the beak. The Toucans may be said to represent in America the Hornbills in India and Africa. Large as is the beak of the Toucan compared with the size of the body, it is in reality very light. Its outer sheathing is somewhat elastic, very thin, smooth, and semi-transparent; and the interior consists of a maze of delicate cells, throughout which the olfactory nerves are multitudinously distributed. The nostrils are basal, the edges of each mandible are serrated, and the colouring of the whole beak is bright, rich, and often relieved by contrasted markings. But these tints begin to fade after death, and become ultimately dissipated. The eyes are surrounded by a considerable space of naked skin, often very richly tinted. The tongue is very long, slender, horizontally flattened, pointed, and, except at its base, horny; it is fringed or feathered along each side. The wings are short, concave, and comparatively feeble. The tail is variable, equal and squared; it is remarkable for the facility with which it can be retroverted or turned up, so as to lie upon the back. This peculiarity results from a modification of structure in the caudal vertebræ, which enables the tail to turn with a jerk by the action of certain muscles, as if it were fixed on a hinge put into action by means of a spring. When the retroversion is accomplished, the muscles which caused it become passive, and offer no resistance to their antagonists, which restore the tail to its ordinary direction. When they sleep they puff out their plumage, they retrovert the tail over the back, draw the head between the shoulders; the bill begins to turn over the right shoulder, and becomes at last buried in the plumage of the back; at the same time the pinions of the wings droop, and conceal the feet. The bird now resembles an oval ball of puffed-up feathers, and is well protected against the cold.