only two toes on the fore-feet. It is to be distinguished, anatomically, from its larger relatives by the complete clavicle, and by the fact that the pterygoids do not meet in the middle line of the skull. The ribs, too, are unusually wide, as in the Whale Neobalaena, and form a bony encasement for the body. It has two small caeca. Of fossil Anteaters but little is known. The most interesting form is Scotaeops, interesting because it has two small back teeth, which are totally lost in its living allies. The huge Patagonian extinct bird Phororhacos, first known by a lower jaw, was at one time regarded as a member of this group on account of the form and edentulous character of the jaw.
Fig. 96.—Unau, or Two-toed Sloth. Choloepus didactylus. × 1⁄5. (After Vogt and Specht.)
Fam. 2. Bradypodidae.—The Sloths, genera Bradypus and Choloepus, come, as already stated, very near to the Anteaters, in spite of their striking difference in appearance. The Sloths are purely arboreal creatures, with strong recurved claws, which serve
