EDENTATA OF THE SANTA CRUZ BEDS. 285 



cranium is of nearly uniform width, the cerebral expansion and the post- 

 orbital constriction being moderate and the broadening of the forehead 

 slight ; the preorbital fossae are shallow and the broad rostrum has nearly 

 parallel sides. 



The basioccipital is short and wide, nearly flat and without keel, and 

 deeply emarginated by the foramen magnum ; the condylar foramen is 

 very large and conspicuous, while the foramen lacerum posterius is still 

 larger and is chiefly, if not entirely, enclosed in the basioccipital ; the 

 foramen magnum is low and wide, of transversely oval shape and with 

 dorsal margin so prominent as to give it something of a tubular form ; 

 the paroccipital processes are small but distinct; the condyles are rela- 

 tively larger than in most other contemporary species and are not so 

 sessile ; they project freely behind the plane of the occiput and form the 

 hindermost part of the skull ; the ventral notch between the condyles is 

 unusually deep, much as in Megalonyx. As a whole, the occiput is high, 

 inclined decidedly forward, bringing the summit on a line with the audi- 

 tory meatus ; it is strongly convex transversely, with median prominence 

 for the vermis ; the inclination of the occiput is more decided than in most 

 of the Santa Cruz Gravigrada, exposing the condyles when the skull is 

 seen from above ; the occipital crest is very distinct, though not very 

 prominent, and dorsally curves forward between the parietals, clearly 

 demarcating them from the supraoccipital. The mastoid portion of the 

 periotic is narrow and rugged and ends ventrally in a short, cylindrical 

 process for the attachment of the stylohyal. The tympanic is, as usual, 

 a mere bony ring, with large and irregular auditory meatus. The basi- 

 sphenoid is long and broad, lying at a lower level than most of the basi- 

 occipital, which descends to meet it ; the presphenoid is concealed by an 

 expansion of the vomer, of which the anterior visible portion is a thin, 

 vertical plate with ventral border descending forward, while the hinder 

 part is a horizontal plate covering much of the presphenoid ; except for a 

 large descending process, the alisphenoid is quite small, but the orbito- 

 sphenoid is relatively large. 



The parietals are large in both dimensions ; for most of its length the 

 sagittal crest is feebly indicated, becoming more distinct anteriorly; the 

 vascular foramina along the parieto-squamosal suture are few. The 

 squamosal is long and low and forms but little of the occipital crest, and 

 develops a prominent tubercle at the postero-inferior angle; the post- 



