1 8 PATAGONIAN EXPEDITIONS: PAL/EONTOLOGY. 



anterior portion, which has a very short contact with the maxillary and 

 an extensive one with the lachrymal, is slender and compressed, but with 

 prominent and somewhat flaring suborbital border ; posteriorly it gives 

 off a large, vertical plate of bone, with much thickened and rugose hinder 

 border ; this plate extends as far as the posterior edge of the zygomatic 

 process and recalls the process seen in the sloths and glyptodonts, but is 

 placed much farther back and is postorbital rather than suborbital. The 

 dorsal border of the jugal is almost straight, rising gradually to the junction 

 with the lachrymal, while the ventral border has a steep inclination down- 

 ward and backward. As a whole, the zygomatic arch is relatively longer 

 than in Tatn and is much less decurved to form the suborbital border ; the 

 jugal makes up a considerably larger share of the arch, extending farther 

 both forward and backward. The arch also curves outward less from the 

 side of the skull, enclosing a longer and narrower temporal fossa, a dif- 

 ference which is increased by the shallower postorbital constriction. 



The lachrymal is quite large, though relatively rather less so than in 

 Tatzt, and less extended posteriorly than in the latter ; this posterior ex- 

 tension is slender and apparently solid, while in the modern genus it is 

 so inflated as to have a hollow appearance. The facial surface of the 

 lachrymal is convex but has not such a swollen appearance, nor is it 

 inflected so far into the orbit, as in Tatu ; it is also less quadrate in shape 

 and ends anteriorly in a point, which is inserted between the frontal and 

 maxillary. The lachrymal foramen is larger and placed more in advance 

 of the orbit than in the existing genus, and behind the foramen is a deep 

 pit, or groove, leading into it, which is wanting in the latter. 



Although the frontals are very long and, as in Tatu, more than twice 

 as long as the parietals, they form relatively little of the cerebral fossa, 

 the postorbital constriction being but little forward of the coronal suture. 

 This constriction is shallower than in the recent genus, and the expansion 

 of the forehead in front of it is less abrupt. The sagittal area is con- 

 tinued forward upon the frontals, ending in ill-defined temporal ridges. 

 On each side of the sagittal area the posterior part of the frontals is 

 somewhat rugose, elsewhere they have a dense and smooth surface. The 

 forehead is quite different from that of Tatn, in which it is vaulted by the 

 great development of the frontal sinuses, while in the fossil the two 

 moderate convexities are separated by a median depression. In one of 

 the skulls (No. 15,565) these convexities are distinct and in the other 



