1 86 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 



it somewhat recurved ; it is narrower than in Nothrotherium, except at the 

 distal end, which has no such emargination of the hinder border. 



The zygomatic process of the squamosal is also much like that of the 

 Brazilian genus ; it is short, laterally compressed and nearly straight, and 

 projects but moderately from the side of the skull ; its base is inflated by 

 a large sinus and notched by the external auditory meatus ; the glenoid 

 cavity is a large and deep oval pit, without definite postglenoid process. 

 The cranial portion of the squamosal is long and low, extending from the 

 occipital crest to the frontal. 



The mandible differs strikingly from that of any of the known Pleisto- 

 cene genera. For most of their length, the short horizontal rami are well 

 separated and form a broad jaw, but in front of the teeth they curve 

 sharply inward to the symphysis, where they are completely fused to- 

 gether. The predentary part of the mandible forms an unusually elon- 

 gate, narrow and bluntly pointed spout or beak, with thin and much 

 elevated lateral borders, so that the dorsal surface is deeply concave ; this 

 spout is longer than in any other known species of the genus. The 

 ventral border of the jaw is strongly sinuous, much more so than in 

 Nothrotherium, convex below the teeth and concave behind them, again 

 becoming convex at the angle. Between the first and second teeth the 

 alveolar border is constricted and below this, on the outer side, is a large 

 and deep pit. The coronoid process arises from the outer side of the 

 ramus, leaving a broad groove between itself and the last tooth; it is 

 high, compressed and recurved and shaped much as in Megalonyx. A 

 broad and deep sigmoid notch separates the coronoid from the condyle, 

 which, as in the latter genus, is set upon a long and slender neck ; it is 

 large, hemispherical, with convex dorsal surface and deeply excavated 

 ventral side. The angular process is a very large hook, similar in shape 

 to that of Megalonyx, though longer and narrower; the inflection of the 

 angle, found in all the Santa Cruz Gravigrada, is especially well marked 

 in the present species. As in the last-named genus, the hinder part of 

 the jaw has a trifid appearance, the coronoid, condyle and angle being 

 quite symmetrically placed and of nearly equal lengths, while in Nothro- 

 therium the small angle gives a very different appearance to this part of 

 the jaw. The postero-external opening of the dental canal pierces the 

 ascending ramus above the base. On the left side the foramen is double, 

 doubtless an abnormality. 



