sometimes exceeds an inch, in the latter it is usually less than one-eighth of that thickness. Note, also, the corresponding contrast in size. The smallest living species is less than a foot in length, whereas the largest known fossil form measured between twelve and thirteen feet in length, or quite as much as the largest rhinoceros. In structure or make-up these giants were sufficiently different from their living relatives to characterize a distinct family, appropriately named by Huxley the Hoplophoridæ, or armor-bearers. Unlike the living armadillos, the back and sides of the body were covered with an inflexible carapace, or coat-of-mail, which, like the same in living forms, was made up of numerous more or less nearly hexagonal tesseræ or plates. In recent forms the armor is divided into two parts: a forward part, covering the scapular or region of the shoulder-blades, and a posterior, covering the pelvic or region of the hips and flanks; between the two a series of mobile bands or zones of plates are interposed transversely, so as to enable the animal to bend its covering upon itself, and thus envelop all the soft parts, and thereby protect itself from enemies almost as effectually as the hedgehog can with its spines. The Hoplophoridæ were provided with an additional rigid, pear-shaped armor-plate or buckler upon the under side of the body, hence they have also been called Biloricata, or two-shielded, in contradistinction to the living Loricata (armadillos), which are shielded only on the back. Head-shields covering the upper part of the head are characters common to both living and fossil forms. The extinct species, with their carapace and plastron, or belly-shield, resembled the snapping turtles in not having the belly-shield to cover more than one-half of the area of the lower side of the body left uncovered by the carapace of the back. The reason why this belly-shield was smaller than the area it partially covered was to allow free and unimpeded movement of the limbs. All that remains of this rigid belly-shield in even the best-armored living species are numerous separated plates, which do not interfere with that flexibility of the walls of the abdomen which is necessary in bending the body when the animal covers itself with its dorsal armor or carapace.
Living species are mostly burrowing in habit. Whether the Hoplophoridæ were burrowers cannot be affirmed, but it is extremely doubtful; though, from the great resemblance of the fore-limbs and claws to those of living species, it is likely that they were able, upon occasion, to dig with great rapidity and dexterity.
I have seen the tongue protruded nearly two inches with great quickness by a young six-banded armadillo; it is tapering and very flexible, and is no doubt used to advantage in capturing insects which
- See Brehm's "Thier-leben," vol. ii., p. 508, for an interesting account of this habit.
most of the materials which I have used in my studies and comparisons have been drawn. From the wealth of materials at his command he has been enabled to present a fuller account of the osteology of these creatures than any other hitherto published. The memoirs of Owen, Lund, Nodot, Huxley and others, have also been consulted.