A NEW MYLODON. 325 



dens in that its outline i.s more that of a figure eight, with a marlced constriction 

 or waist which divides the tooth into a sUghtly larger anterior lobe with the 

 outer corner in advance of the inner, and a smaller posterior lobe only slightly 

 asymmetrical. The long axis of the tooth coincides with that of the tooth- 

 row, and measures 30.5 mm.; the breadth of the anterior lobe is 20 and of the 

 posterior 15 mm. In M. harlani and in M. renidens the tooth has a slightly 

 concave external outline with a more marked internal concavity, but the pos- 

 terior lobe thus defined does not expand again terminally, and the same is appar- 

 ently the case in the Colorado skull. 



The mandible in lateral outline resembles that of M. robustus, except that 

 owing to the extreme narrowness of the skull, the symphysis is less broadly 

 truncate. The anterior external openings of the dental canal are three in num- 

 ber, arranged in longitudinal series. The anteriormost is very large, the two 

 others much smaller and subequal. The vertical diameter of the first is 14 mm., 

 of the smaller ones about 7 mm. In Paramylodon the middle foramen is the 

 largest. The predental part of the jaw is much narrowed as seen from above, 

 in marked contrast to the broad square termination of M. robustus. This fact 

 points to a narrow extensile tongue, for a browsing, rather than a grazing habit, 

 which makes use of a broad symphysis for cropping. The tip of the jaw is 

 slightly damaged. 



As already noticed, the ramus tapers but little in side view, from base of 

 the coronoid process forward, in marked contrast to Paramylodon in which 

 the jaw is but one half as deep at the symphysis as at the base of the coronoid 

 process. Directly above the posterior end of the symphysis, the tip of the jaw 

 slopes upward above the level of the toothrow so that the depth at the extreme 

 tip is quite equal to that at the base of the coronoid process, nearly 105 mm. 

 The condyle is slightly above the level of the toothrow, with its long axis nearly 

 transverse. 



The toothrows of the lower, as of the upper jaw, converge posteriorly. 

 The extreme alveolar length of the row is 156 mm. The four teeth are set close 

 together and though of the general Mylodon type, differ in details from those 

 of other species known. 



The anteriormost lower toolh projects some 24 mm. above the alveolus, 

 and about half that distance above the crowns of the succeeding teeth. In 

 Paramylodon this tooth projects much farther above the alveolus. Its outline 

 is elliptical in section, scarcely reniform, since the inner side is nearly flat instead 

 of concave. The crown presents an anterior and a posterior beveled surface, 



