57^ Bulletin American Museum of Natural History, [Vol. XIX, 



forward and upward in a small canal at the upper border of 

 the pterygoid, partly defined by the overhanging projection of 

 the temporal. The posterior upper border is marked by deep 

 channels and ridges. 



The frontal is the largest bone of the skull, forming the 

 middle half of the upper surface of the cranium, articulating 

 in front with the nasal, maxillary, and lachrymal, below with 

 the lachrymal, maxillary, and orbitosphenoid, and behind with 

 the parietal and squamosal. Externally it presents a smooth 

 surface of irregular curves expanded in front at the postorbital 

 process, extending downward and inward to unite with the 

 maxillary below the lachrymal, with a deep overhanging fold 

 exterior to the optic foramen, as in Glyptodon. Above the 

 optic foramen it descends outward slightly to unite with the 

 orbitosphenoid. 



The orbitosphenoid is not suturally defined but represents a 

 depressed area, bounded on the outside by an overhanging 

 wall of the frontal containing the optic foramen and foramen 

 rotundum separated by a thin wall of bone. 



The lachrymal presents an irregular outline, the superior 

 border of which rises anteriorly above the malar in a rugose 

 surface, in the centre of which is the lachrymal foramen. The 

 posterior portion is much thinner and extends back in a 

 truncated point to a line connecting the postorbital process 

 of the frontal and the posterior margin of the last molar. 

 Below the lachrymal foramen there is a deep rounded pit, 

 with a raised cone in the center, for articulation with the 

 malar. 



That part of the maxillary presented in side view is of a 

 quadrate form, convex on the outer surface, and extends 

 nearly to the anterior end of the nasals, with which it forms 

 a vertical cross-section. Posteriorly it unites with the orbito- 

 sphenoid at the beginning of the canal that leads into the 

 optic foramen; above, with the lachrymal, frontal, and nasals. 

 The malar process is a stout projection set obliquely to the 

 maxillary, forming the anterior buttress of the malar and 

 enclosing the infraorbital foramen. Across the middle of the 

 maxillary, beginning above the infraorbital foramen in a 



