66 EXPLANATION OP THE PLATES. 



PLATE XV. 



Megatherium. Pigs. 1, 2, are two-thirds tlie diameter of nature ; Fig. 3, one-third ; and Fig. 4 

 is of the natural size. 



Figs. 1, 2. Outer and upper views of the left side of the lower jaw, being part of a specimen from 

 Skiddaway Island, and now belonging to the National Institute collection. 



Fig. 3. Temporo-occipital fragment of a cranium, from the right side. 



Fig. 4. Fragment of a molar tooth. 



PLATE XVI. 



■ All the figures of this plate are of the natural size ; and to insure their accuracy they were drawn by 

 the author. 



Megaxonyx Jeitersonii. Figs. 1-6. Transverse sections of first superior molar teeth. 



Fig. 1. From one of the specimens contained in the skull of Dr. Owen's collection. 



Fig. 2. From the specimen contained in the skull of Dr. Dickeson's collection. 



Fig. 3. From an isolated specimen, in Dr. Dickeson's collection, from near Natchez, Mississippi. 

 This section is from the tooth which was supposed to characterize the Megalonyx potens. 



Fig. 4 From a specimen, in Professor Silliman's collection, from Memphis, Tennessee. 



Fig. 5. From a specimen, in Col. Wailes' collection, from Adams Co., Mississippi. 



Fig. 6. From a specimen, in Professor Wyman's collection, from Natchez Bluffs, Mississippi. 



Fig. 1. Transverse section of a cast in clay of the first inferior molar alveolus of the right side, taken 

 from the specimen of the lower jaw, of Dr. Owen's collection. 



Fig. 9. Transverse sections of the posterior four superior molars of the right side ; from the skull in 

 Dr. Owen's collection. The series a, b, c, d, is directed from behind forwards. 



Fig. 10. A similar representation to the preceding figure ; from the skull in Dr. Dickeson's collection. 



Fig. 11. Section of a fourth upper molar tooth, from a specimen in the collection of Col. Wailes, 

 from Adams Co., Mississippi. 



Fig. 12. Section of a third ? upper molar, from a specimen in Professor Wyman's collection, from 

 Natchez Bluffs, Mississippi. 



Fig. 13. Section of a molar of Megalonyx Jejfersonii ?, in Professor Wyman's collection, from Tus- 

 cumbia Co., Alabama. 



Fig. 14. Section of a second upper molar, in Professor Wyman's collection, from Natchez Bluffs, 

 Mississippi. 



Figs. 16, n. Sections of the second and last lower molar teeth, from the specimens in the lower jaw 

 of Dr. Owen's collection. 



Megalonyx dissimilis. Fig. 8. Transverse section of a first inferior molar, in Dr. Dickeson's col- 

 lection, from near Natchez, Mississippi. 



Fig. 15. Section of a last superior molar, which accompanied the last-mentioned specimen. 



Beeptodon priscus. Fig. 18. Transverse section of the molar tooth upon which a new genus and 

 species have been proposed. The specimen, in Dr. Dickeson's collection, is from near Natchez, Mis- 

 sissippi. 



Mylodon Harlani. Fig. 19. Sections of the right lower molar teeth, contained in the fragment of 

 a jaw, found at Big-bone-lick, and now in the possession of the New York Lyceum of Natural History. 



Fig. 20. Section from two fragments of a last lower molar tooth, in Col. Wailes' collection, from 

 Mammoth Ravine, Mississippi. 



Fig. 21. Fragment of a first lower molar tooth, from a specimen discovered by Captain Bowman, 

 D. S. A., in the sands of Ashley river. South Carolina, a. broken longitudinal surface ; S. lateral view ; 

 c. transverse section. It was upon this fragment that Eubradys antiquus was erroneously proposed. 



