EDENTATA OF THE SANTA CRUZ BEDS. 121 



process other than a low, rough ridge ; the anterior portion of the bone 

 has the same peculiar fusiform shape seen in Glyptodon, tapering to a sharp 

 edge. The tympanics have not been found. Little of the basisphenoid 

 is exposed to view ; the visible part is broad and thick, contracting anter- 

 iorly, while the ali- and orbitosphenoids are reduced to small proportions 

 by the encroachment of the maxillaries. 



The parietals are large and form nearly the entire roof of the cerebral 

 fossa; most of their surface is very rough and is perforated by several 

 large and conspicuous venous foramina. For their whole length, the 

 parietals support a moderately prominent sagittal crest. The squamosal 

 is low, but elongate, apparently articulating with the frontal ; the glenoid 

 cavity has already acquired the peculiar form seen in Glyptodon, being a 

 slightly convex ridge, which presents obliquely downward and backward ; 

 there is no postglenoid process, but behind the cavity, so called, is a 

 large, deep fossa, in the roof of which are venous foramina. The zygo- 

 matic process has a rather short and slender free portion, which exten- 

 sively overlaps the jugal, ending in a rounded anterior projection, which 

 fits into a notch of the jugal. The latter is a long, stout and laterally 

 compressed plate, which extends posteriorly beneath the zygomatic pro- 

 cess of the squamosal nearly to the glenoid cavity, and anteriorly is pro- 

 duced downward upon the great descending zygomatic process of the 

 maxillary, though not reaching quite to its free end ; the postorbital pro- 

 cess is hardly more than an angulation. The lachrymal is large and rests 

 upon the zygomatic process of the maxillary, articulating with the frontal 

 and jugal ; the foramen is large and conspicuous and placed well in front 

 of the orbit. 



The frontals are long and broad, slightly narrowed by the postorbital 

 constriction and expanding over the orbits ; the postorbital processes are 

 very short, and the temporal ridges are hardly visible, though the sagittal 

 crest is often continued over upon the frontals. The frontal sinuses are 

 sufficiently developed to make the forehead convex, but there are great 

 individual differences in the degree of prominence thus produced. In 

 certain specimens, presumably old males, the inflation of this whole region 

 is such as to suggest an incipient stage of the development which gives 

 such a grotesque appearance to the facial region of the Pampean Sclero- 

 calyptus. Within the orbit there is an oblique ridge upon the frontal, 

 which passes downward and backward, ending in a broad, compressed, 



