184 ARMOURED EDENTATES CHAP. 
On the manus, the three inner digits have powerful claws. This 
animal, too, was Pleistocene in time. The Megatheriidae had, 
however, small as well as gigantic forms. 
The genus Zamicrus had a skull no bigger than that of a 
Sloth, while Nothrotherium was also a comparatively small 
creature ; the teeth of the latter genus are reduced to 4. 
The extinct group of the Glyptodontidae comprises large 
creatures with a dense covering of bony scutes which are arranged 
in a tesselated fashion, and thus form an immobile armature of 
immense strength. In correspondence with this massive carapace 
the dorsal vertebrae have fused together, and the lumbar vertebrae 
form a series ankylosed to each other and to the following sacrals. 
These creatures are all South American. 
Glyptodon, the genus which gives its name to the family, is 
known from numerous remains in South America, and also from 
Fic. 106.—Glyptodon clavipes. x js. (After Owen.) 
1 
so far north as Texas and Mexico. It grew to be as long as 16 
or 17 feet. In the skull there is an exceedingly long 
downward process of the zygomatic arch, as in Sloths, the arch 
itself being complete. The process extends so far down as to 
reach a point about on a level with the middle of the lower jaw. 
The nasals are short or rudimentary. As in Myrmecophaga, the 
pterygoids enter into the formation of the bony palate. The 
lower jaw has a spout-shaped extremity, and, behind, it rises into 
an enormous vertical branch as high as the front part of the jaw 
is long. There are eight teeth in each half of each jaw. As in 
