170 FOSSIL ANTEATERS CHAP. 
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. 
Fam. 2. Bradypodidae.—The Sloths, genera Bradypus and 
Fic. 96.—Unau, or Two-toed Sloth. Choloepus didactylus. x 4. 
(After Vogt and Specht.) 
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 
