EXPLANATION OF THE PLATES. 



PLATE I 



Megaxonyx Jeffersonii. View of the left side of the slvuU, with the lower jaw ; two-thirds the 

 diameter of nature. From the specimen of Dr. Owen's collection. 



The lower portion of the outer side of the first molar alveolus of the upper jaw, destro3'ed in the 

 specimen, has been represented in its restored condition. The malar bone is lost ; and so, also, are the 

 first and third molar teeth of the lower jaw. 



PLATE I r . 



Megalonyx Jeffersonii. View of the upper part of the same skull as that represented in the pre- 

 ceding plate. Two-thirds the diameter of nature. 



The malar bones and the right zygomatic process are lost. 



PLATE III. 



Megalonyx Jeffersonii. View of the base of the skull ; from the same specimen as the preceding 

 plates. Two-thirds the diameter of nature. 



The malar bones, pterygoid processes, the right zygomatic process, the left second molar tooth, and 

 the last right molar tooth are lost. 



PLATE IV. 



Megalonyx Jeffersonii. View of the left side of the skull ; two-thirds the size of nature. From 

 the specimen of Dr. Dickeson's collection. 



The first molar alveolus has been represented in its perfect condition, though broken away e.xternally 

 in the specimen. The malar bones, zygomatic processes, and pterygoid processes are lost. 



PLATE V. 



Megalonyx Jeffersonii. Figures two-thirds the diameter of nature. 



Fig. 1. Upper view of the right side of the lower jaw, from the same specimen as that represented 

 in Plate I. 



Fig. 2. Inner view of the same specimen. 

 The first and third molar teeth are lost. 



