Page:Popular Science Monthly Volume 13.djvu/157

Rh conclusions; not only do the vertebral centra become more rudimentary as the young condition is departed from in the life-history of the individual tortoise, but the centra also become successively more rudimentary as we pass from the less completely armored genera Sphargis and Trionyx, to the more completely armored Testudo and Cistudo.

Like the tortoises, our huge animal had an arrangement of the neck vertebræ whereby he could withdraw his head slightly backward in case of an attack, so as to bring his head-shield to fit closely against his carapace. The atlas or first joint of the neck was separate, the next four were united, the sixth was separate, and a "trivertebral bone," which seems to have taken a share in the neck as well as in the thorax, followed next, and probably was the bone which enabled the creature to retract its head somewhat; next followed ten united rib-bearing trunk vertebræ, which Prof. Burmeister has aptly called the "dorsal tube" (see cross-section, Fig. A). Succeeding the "dorsal tube" are eight lumbar and probably eight sacral vertebræ firmly united together and to the ilia; following these, come twenty-one caudal or tail bones, footing up a total of fifty-six segments in the entire spinal column, which is not far from the number found in living species, though only about one-fourth as many are united together in them as in our fossils. The plates of the carapace were united by suture in the fossil species, rendering the armor as rigid as the carapaces of land-tortoises. In living forms, the plates, in some species at least, are slightly separated by intervening integument, rendering the armor more or less flexible throughout.

The remains of the Hoplophoridæ—better known by Prof. Owen's older name as the Glyptodons—have been found mostly in the bone-caves of Brazil, and in the alluvium and pampean Pliocene of Eastern and temperate South America. The finest collection of their remains in existence is in the Public Museum of Buenos Ayres. They were probably contemporaneous with some of the great Carnivora, whose remains have also been found in the caves. One of these, the sabre-toothed tiger (Machairodus), would, no doubt, have frequently rendered the almost invulnerable armor of the giant (but perhaps harmless) armadillo of great service, within which he could feel himself secure from the attacks of such a well-armed foe.

The restoration is one-eighteenth of the natural size, and is based on the figures in Burmeister's work. It is believed to be approximately correct, since nothing was needed to make the originals assume the appearance of life except to clothe the skull and neck with flesh, and furnish the extremities with claws and hoofs, muscles and tendons. The animal was between nine and ten feet in total length, and stood about four and a half feet high at the highest part of the back. Prof. Burmeister has christened the species Panochthus tuberculatus.