EDENTATA OF THE SANTA CRUZ BEDS. 325 



restrains. The alisphenoid, though large, is almost -confined to the ven- 

 tral aspect of the cranium, where it follows the course of the squamosal 

 and has a short suture with the parietal and a longer one with the frontal ; 

 the descending process is large and its ventral border is thickened and 

 cancellous. The outer portion of the relatively large orbitosphenoid is 

 depressed by two concavities leading respectively to the optic foramen and 

 foramen lacerum anterius. 



The frontals are very large and have an inflated look, which indicates 

 the presence of large sinuses ; the postorbital foramina are uncommonly 

 large and conspicuous ; the sutures with the maxillaries are relatively long 

 and straight, with a wide, shallow notch between them for the nasals. 

 The squamosal is relatively small and forms no part of the occipital crest 

 and has no connection with the exoccipital, from which it is separated by 

 the periotic ; the broad, deep notch of the ventral border for the auditory 

 meatus produces quite a distinct posttympanic process and the whole 

 infero-lateral angle of the bone is rugose ; the glenoid cavity is but mod- 

 erately concave, but extends farther upon the zygomatic process than in 

 any of the other genera ; this process is short and rather slender and has 

 a' distinct downward inclination. Although the jugal has been lost, its 

 great length is demonstrated by the space between the zygomatic processes 

 of the squamosal and maxillary. The lachrymal is of the ordinary type. 



The nasals have quite a characteristic form ; they are widest posteriorly, 

 contracting forward to the narrowest part and thence broadening slightly 

 to the anterior end ; along the median line, where the two nasals meet, is 

 a narrow and shallow, but well defined groove ; at the forward end each 

 nasal has a long lateral process, defined by a deep notch, while the median 

 part is obliquely truncated, forming with its fellow a blunt point. The 

 anterior nares are broad and low, with sides and top regularly curved 

 and describing somewhat more than half of a transverse ellipse. 



The maxillary is very long, especially the preorbital portion, which is 

 for the most part convex, the preorbital fossa being shallow and incon- 

 spicuous and dying away dorsally. Owing to the narrowness of the 

 nasals and the curvature of the maxillaries, the latter form more than half 

 of the roof of the nasal chamber, and their anterior edge is thin, except 

 at the infero-lateral angles where they are much thickened to form the 

 facets for the premaxillae. The large and heavy zygomatic process is per- 

 forated by a short infraorbital canal, the anterior opening of which is 



