620 LAND MAMMALS IN THE WESTERN HEMISPHERE 



The skull was remarkably short, broad and high, the facial 

 region being especially abbreviated ; the cranium, though 

 forming the greater part of the skull, was yet small in compari- 

 son with the size of the animal ; it had a distinct, though not 

 prominent, sagittal crest. The occipital surface was inclined 

 forward and had a very elevatfed position, the condyles being 

 near the top of the head and raised very far above the level of 

 the teeth. The orbits were relatively small, more or less com- 

 pletely encircled with bone and as near to the top of the head as 

 they could be brought ; this was to make room for the extremely 

 high teeth, which required a great depth of jaw; the elevation 

 of the whole cranium left unlimited space for the jaws beneath 

 it. The zygomatic arches were strong and curved out widely 

 from the sides of the skull ; beneath each eye was given off a 

 . very long descending process which projected downward, out- 

 side of the lower jaw. In most of the species the upper pro- 

 file of the skull was nearly straight, but in ^Panochthus it 

 descended very steeply from the forehead to the nose. The 

 forehead was dome-like and the nasals extremely short. Si- 

 nuses were extensively developed, especially in the frontals, and 

 in ^Sclerocalyptus the bones around the nostrils were grotesquely 

 inflated. The two halves of the. lower jaw were fused together, 

 and the symphysis was prolonged into a short, wide spout, 

 which projected considerably in advance of the upper jaw, 

 showing that the soft parts of the muzzle must have had a 

 corresponding extension. The horizontal portion of the lower 

 jaw, carr3dng the teeth, was short and very deep ; the posterior, 

 ascending portion had a forward inclination and was very high. 

 The skeleton of the Pleistocene fglyptodonts was unique 

 among mammals, though evidently a modification of the ar- 

 madillo type. The extreme modification was conditioned by 

 the enormous weight of the carapace, which the skeleton had to 

 support. The neck was very short, made up of short vertebrae, 

 which were extensively coossified; the atlas was always free, 

 but the axis was fused with a varying number of the succeed- 



