iz THE DESEADO FORMATION OF PATAGONIA 
on the sides of the skull, bounding the lower part of the 
orbit, and having a short zygomatic process. The small 
lachrymal is but little exposed on the exterior surface of 
the skull, the lachrymal pit being well inside the orbit. 
The zygomatic arches are broad and heavy, and composed 
mostly of the wide jugal bones. The palate is highly arched 
and relatively narrow, the crowns of the premolars and 
molars projecting inward over it, thus narrowing it still 
more. It extends back well beyond the last molar. The 
large tympanic bullae are hollow, and the cavity in the 
squamosum seems to be reduced in size, as compared with 
Rhynchippidae or Nesodontidae. The occipital condyles are 
set well apart and are sessile; and the paroccipital proc- 
esses are long and slender. 
The atlas, axis and cervical 3 are associated with the 
skulls. The atlas is short, heavy, and has the anterior 
cotyles broad, deeply excavated and wide apart; while the 
posterior cotyles are nearly flat, and high as well as wide. 
The transverse processes are only moderately wide, but are 
very heavy, especially along the posterior margin. The 
centrum of the axis is flattened, the neural canal, wider 
than high, and the neural spine of moderate height. The 
anterior cotyles are broad and moderately convex, and the 
odontoid process is a stout peg-like process, somewhat 
higher than wide. Slender transverse processes project 
sharply from the centrum, and have at their bases a large 
canal for the vertebral artery. Cervical 3 is shorter than 
the axis, has a less depressed centrum, a small neural spine, 
and short wide transverse processes. 
Though I have skulls and jaws to represent some twenty- 
five individuals, no limb material was found in direct asso- 
ciation with any of them. However we did find a humerus, 
radius and ulna on the same level and about fifteen feet 
from one of the skulls, and as it corresponds in size, and as 
humeri of this type are the most abundant skeletal bones 
found (as is also the case with the skulls), I have considered 
