1 6 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. 



The parietals are relatively long, extending forward to the postorbital 

 constriction, where, on the dorsal side, they diverge to receive the pos- 

 terior ends of the frontals. As already mentioned, the parietals support 

 throughout their length a thin sagittal crest, which is low anteriorly and 

 rises gradually behind, where it becomes very high. In this posterior 

 region the parietals are pierced by several conspicuous vascular foramina. 

 The squamosal extends well upward upon the side of the cranium, greatly 

 narrowing the parietal in this region, but is widely separated from the 

 frontal. The glenoid cavity is quite equine in character and may be 

 described in the words which Flower ('85, 187) has applied to that of the 

 horse; it is "greatly extended transversely, concave from side to side, 

 convex from before backward in front and hollow behind." The only 

 difference is that the anterior convexity is less prominent in the Santa 

 Cruz genus. The postglenoid process is long, thick and spike-shaped, 

 rhinocerotic rather than equine in character, but relatively shorter and 

 more massive than in existing rhinoceroses. The posttympanic process, 

 which is small, but well defined, is applied closely to the periotic and 

 widely separated from the postglenoid. The zygomatic process is rather 

 short, arching out boldly from the cranium ; it is laterally compressed and 

 thin, but quite broad dorso-ventrally, this breadth diminishing anteriorly 

 as that of the jugal increases. The latter is elongate, extending posteriorly 

 to the glenoid cavity and anteriorly to the lachrymal ; the free portion is, 

 like the zygomatic process, laterally compressed, but the suborbital por- 

 tion is considerably thickened. The postorbital process is broad and 

 prominent, but not very long ; it unites suturally with the much longer 

 process of the frontal. The lachrymal is large and considerably expanded 

 upon the face, forming part of the inferior and almost all of the anterior 

 wall of the orbit, and even some of the dorsal margin ; it articulates with 

 the jugal, maxillary and frontal, but is widely removed from the nasal ; 

 the foramen is quite large and entirely external in position, and the spine 

 is a low tubercle. 



The frontals are very large and form a broad, lozenge-shaped and nearly 

 plane forehead ; they are widest over the orbits, narrowing gradually to 

 the sutures with the maxillaries and nasals, which form a nearly straight, 

 transverse, though somewhat irregular line. The frontals expand very 

 abruptly in front of the postorbital constriction and the temporal ridges, 

 which diverge from the sagittal crest, take an almost transverse course ; 



