62 EXPLANATION OF THE PLATES. 



PLATE VI. 



Megalonyx Jeffeesonii. Fig. L View of the hard palate and teetb, from the skull represented in 

 Plate IV. Three-fifths the diameter of nature. (The anterior portion of the figure is that to the left 

 of the plate.) 



The first molar teeth of both sides, and the posterior two of the left side are not contained within 

 their sockets, and all except one of the former are lost in the specimen. 



Fig. 2. Anterior view of the skull represented in Plates I-III. One half the diameter of nature. 



On both sides of the specimen the external portion of the first molar alveolus is destroyed, but on the 

 right side of the figure it is represented in a restored condition. 



Fig. 3. Posterior view of the skull represented in Plates I-III. One half the diameter of nature. 



The remaining figures are of the natural size. 



Fig. 4. Inner view of a first upper molar tooth of the right side. From a specimen, in Prof. Silli- 

 man's collection, found at Memphis, -Tennessee. 



Fig. 5. View of the triturating surface of the same specimen as the preceding figure. 



Fig. 6. Inner view of a first upper molar tooth of the left side. From a specimen, in Dr. Dickeson's 

 collection, found in a ravine near Natchez, Mississippi. 



Fig. "I. View of the triturating surface of the same specimen as the preceding figure. 



Figs. 6 and "I are from the specimen which was formerly thought to characterize a species of Mega- 

 lonyx, to which the name of M. potens was given. - 



Fig. 8. View of an isolated molar tooth, probably not belonging to Megalonyx Jeffersonii. From 

 a specimen, in Prof. Wyman's collection, found in Tuscumbia Co., Alabama. 



Fig. 9. View of the triturating surface of the same specimen as that represented in the preceding 

 figure. 



Fig. 10. Posterior view of the last lower molar tooth of the right side, from the specimen repre- 

 sented in the jaw in Plates I and V. 



Fig. IL View of the triturating surface of the same specimen as that represented in the preceding 

 figure. 



PLATE VII. 



Megalonyx Jeffeesonii. All the figures are from specimens in Dr. Owen's collection, and are 

 one half the diameter of nature, except T and 8, which are from a specimen in Dr. Dickeson's col- 

 lection, and measure two-thirds the diameter of nature. 



Fig. 1. Inferior view of the atlas. 



Fig. 2. Anterior view of the same specimen. 



Fig. 3. Lateral view of the axis. 



Fig. 4. Lateral view of one of the posterior cervical vertebrae 



Fig. 5. Inferior view of the last sacral vertebra. 



Fig. 6. Anterior view of an anterior caudal vertebra. 



Fig. 1. The hyoid bone. 

 . Fig. 8. Lateral view of the same specimen. 



PLATE VIIT. 



Megalonyx Jeffeesonii. Figures 1 to 5 inclusive, are one-third the diameter of nature, and the 

 remainder are one-half. Figures 1, 2, 9, 10 A, 11 A, 12 A, and 13 A, are from specimens in Dr. 

 Dickeson's collection; 3 and 4 are from specimens of Mr. Wetherill's collection; and the remaining 

 ones are from specimens of Dr. Owen's collection. 



