1903.] Brown, A New Genus of Groutid Sloth. 579 



face may be divided into three regions: the anterior, which, 

 from the second molar to the symphysis, is convex vertically 

 and concave horizontally; the middle, from the second to the 

 last molars, which is nearly fiat; and the posterior, back of 

 the last molar, which is deeply concave. The lower border is 

 rounded and thickened below the dental series, thinning out 

 anteriorly and posteriorly. The upper or alveolar border is 

 wide and rugose, and on the outside of the jaw there is a 

 shallow depression extending the entire length below the 

 alveoli. 



The anterior expanded end presents an obliquely sloping 

 symphysis , nearly half as wide as deep, extending anteriorly 

 in a deep rounded border. From a front view this anterior 

 border has the outline of a keel-like projection extending for- 

 ward in the middle of the jaw. Below this keel is a rounded 

 mammilloid process, much less prominent than in Mylodon. 

 The portion of the jaw in front of the first molar is longer 

 than in M. robustus and the width of the expanded portion is 

 much less. The dental region is not nearly so deep as in 

 Mylodon. 



The posterior part of the jaw is expanded into a thin deep 

 plate, divided into the coronoid, condyloid, and angular pro- 

 cesses. The point of the angular process is broken off; the 

 lower margin is convex and the inner side presents a deep 

 concavity bounded below anteriorly by the inferior inflected 

 border of the process and a ridge that extends forward and 

 upward to near the alveolus of the last molar; below, posteri- 

 orly, the inner border is roughened by processes; above, it is 

 bounded by the rounded border of the dental canal. The 

 outer surface of the angle is convex and rugose. 



The coronoid process is broken at the point but seems to 

 have been nearly straight, slightly convex on the anterior 

 border. 



The condyle is long and narrow, set obliquely to the vertical 

 plane of the coronoid. The greater part of the condyle over- 

 hangs the supporting plate of bone, only about one fourth 

 extending on the outer side of the ramus. It rises from a 

 triangular base, the outer angle of which begins below the 



