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VIII complete the arcade. The premaxillaries are very small, and are usually lost in dried skulls. Coupled with these points of likeness are some differences. The lower jaw, for instance, has a well-marked coronoid process. The pterygoids do not meet in the middle line. The teeth are five or four in each half of each jaw. There is no trace of a second set.

A peculiarity of the Sloths is the enormous number of dorsal vertebrae. There are twenty-three of these in Choloepus hoffmanni, but only fifteen to seventeen in the Three-toed Sloth, Bradypus. As in other American Edentates, the acromion joins the coracoid. This connexion occurs in both the Two-toed and the Three-toed species. The limbs of these creatures are very long, a concomitant of an arboreal life. The femur has no third trochanter. The genus Bradypus, which by reason of the fact that it has not lost the third toe on the manus seems to be more primitive than Choloepus, shows another structural feature which does not bear out this conclusion. The trapezoid and the os magnum of the carpus are united, while in Choloepus they are perfectly distinct bones.

The intestine has no caecum.

There are several species of Sloths. Eminently perfect though the organisation of the Sloth in relation to its particular surroundings appears to us, Buffon selected the animal as the very type of imperfection in nature. "One more defect," he wrote, "they could not have existed."

'''Fam. 3. Dasypodidae.'''—The family Dasypodidae or Armadillos contains a considerable number of genera. Tatusia, Tolypeutes, Dasypus, Xenurus, Priodon, and Chlamydophorus. They have all a more or less rigid covering of bony plates imbedded in the skin, which are not in the least comparable with the scales of the Manis. Save the Whales, in one or two genera of which traces of a dermal armature exist, the Armadillos are unique among existing mammals in this particular. The term "Edentate" is especially inapplicable to the Armadillos; the genus Priodon may have more than forty teeth in each jaw; a total of ninety was found in one specimen examined by Professor Kükenthal. In the tendency of the teeth to multiply, we have another example of a state of affairs which characterises so many Whales. Generally, however, seven to nine is the number of teeth in each