In the Pleistocene cavern-deposits of Brazil, but still more abundantly in the fluviatile deposits which cover the country in the neighbourhood of Buenos Ayres, are found the remains of some of the most remarkable forms of mammals yet discovered, the Glyptodonts, which may be regarded as forming a separate extinct family. They differ from the existing _Dasypodidæ_ in their large size, and in having the carapace composed of a solid piece (formed by the union of a multitude of bony dermal scutes) without any movable rings, and in usually having also a ventral piece or plastron. The facial portion of the skull is very short. A long process of the maxillary bone descends from the anterior part of the zygomatic arch. The ascending ramus of the mandible is remarkably high. The teeth are ⁸⁄₈ in the known species, all much alike, having two deep grooves or flutings on each side, so as to divide them into three nearly distinct lobes (Fig. 68). The vertebral column is almost entirely ankylosed into a solid tube, and there is a complex joint at the base of the neck, to allow of the head being retracted within the carapace. The limbs are very strong, and the feet short and broad, resembling externally those of an elephant or tortoise. This family is mainly characteristic of the southern half of the American continent, but some species of the type genus ranged into Texas and Mexico. Many species of the family have been described and figured, especially by Burmeister (in the _Annales del Museo publico de Buenos Aires_), among which the following may be noticed. _Hoplophorus_ is characterised by the sculptured and frequently thin scutes of the carapace, those of the periphery being flat, and not raised into prominences. The caudal sheath has several overlapping movable rings at the base, and ends in a long subcylindrical terminal tube similar to the one represented with the carapace of _Glyptodon_ in Fig. 69, which in all probability really belongs to the genus under consideration. Each foot has four complete digits, and the humerus has an entepicondylar foramen. Most of the species are of medium size. Part of a caudal tube from Uruguay described as _Eleutherocercus_ indicates, however, a much larger allied form, in which the tail appears to have had a number of stout bristles protruding from the joints between the scutes. _Panochthus_ comprises very large Glyptodonts, distinguished by the great thickness of the scutes of the carapace, which are ornamented with tubercles. The termination of the caudal sheath forms a tube bearing large radiated tubercles. _Euryurus_ is distinguished by the radiate sculpture of the scutes of the carapace. _Dœdicurus_, of which one species was about twelve feet in length, also has a rugose sculpture on the carapace; but the termination of the caudal tube is expanded into a club-like shape, flattened from above downwards, and covered with tubercles mingled with a few large radiate discs, which, as in