MYLODON. 4'^ 



is convex and slightly impressed longitudinally at several points. The outer side 

 is longitudinally fluted (Fig. 9), and in the specimen anteriorly it presents an 

 irregular nodulated line apparently the result of disease in .the dental pulp. The 

 anterior border is narrow and smooth ; and the posterior border is obtuse, and at 

 the triturating surface is worn away for several lines. 



As above mentioned incidentally, the molar tooth of Ereptodon priscus has the 

 same structure as the teeth of McijaJonyx ; but a peculiarity observed in the speci- 

 men is the nearly unifoi'm thickness of the harder dentine and cementum all 

 round. 



HIYLODOIV, Owen. 

 ITIylodoii Karlani, Owen. 



In the American Journal of Geology,^ and subsequently in the Medical and 

 Physical Researches," Dr llai'lan described and figured a fragment of the lower jaw 

 of an extinct bradypoid animal, which he referred to the Mc(jalonyx laqueatus, but 

 Professor Owen^ determined it to belong to the genus Mylodon, and dedicated the 

 species to Dr. Harlan. 



The specimen referred to belongs to the Cabinet of the Lyceum of Natural 

 History of New York, and has been kindly loaned to me for examination. It was 

 found at Big-bone-lick, Kentucky ; and it is unchanged in texture. Its form (PI. 

 XIV, Figs. 1, 2) is like that of the corresponding portion of the lower jaw of the 

 Mylodoii rohicstu-s. 



Within the first alveolus of the specimen is a small fragment of the appertaining 

 molar, which, though mutilated is sufiiciently perfect to indicate its form in trans- 

 verse section. (PI. XVI, Fig. 19, a.) This is reniform, with the long diameter 

 antero-posterior, and measuring twelve and a half lines. The inner side is concave, 

 and the outer one convex; and the short diameter of the tooth is about seven and 

 a quarter lines. 



The second molar in section (PI. XVI, Fig. 19, h) is quadrate with rounded 

 angles. Its postero-internal portion is most prominent, and its outer side is convex 

 while the other three sides are concave. The antero-posterior diameter is eight 

 and a half lines, and the transverse diameter ten lines. 



The third molar (PI. XVI, Fig. 19, c) is transversely oblong quadrilateral, with 

 rounded angles. It is obliquelj^ situated in the jaw ; has the anterior and posterior 

 sides concave, the outer one convex, and that internal nearly a plane. Its antero- 

 posterior diameter is seven and a half lines ; its transverse diameter fourteen lines. 



The last tooth (PI. XVI, Fig. 19, d) of the series is intermediate in form to that 

 of Mylodon rohustus and M. DariolniL In transverse section it presents an irregular 

 dumb-bell outline. The anterior lobe is most produced antero-externally, while that 

 posterior is most produced postero-internally. Anteriorly the tooth is obhquely 



» I, Y4, PI. iii, Figs. 1, 2, 3. ' 334, Tl. xv, Figs. 2, 3, 4. 



» Zool. of the Voyage of the Beagle; Foss. Mam., 68. 



