46 BKEPTODON. 



verse section of a tooth, figure 13, whicli so closely resembles that of the tooth 

 above described, that it might be readily taken for it, except it is larger. Cuvier 

 never alludes to this figure, but in the references to Plate CCXVI, of the Atlas to 

 the posthumous edition of the Ossemens Fossiles, it is stated that "la figure 13 est 

 vraisemblablementla coupe horizontale de la dent precedente, pour montrer son epais- 

 seur." This is most probably a mistake, for it is impossible that an outline like 

 that of figure 13 could be produced from figure 14, which represents pretty cor- 

 rectly the first molar, most probably of the lower jaw, of M. Jeffersonii. Figure 13 

 I suspect was drawn from a distinct tooth, which was subsequently mislaid and 

 forgotten. If, however, this view be incorrect, it must be acknowledged that the 

 two figures above mentioned have no correspondence in form with each other, while 

 they exhibit an extraordinary resemblance to distinct forms of teeth existing in 

 nature, one of which had never been seen by the artist.^ 



The other tooth referred to as probably being a fifth upper molar (PI. XIV, 

 Figs. 7, 8) is compressed ovoidal in section (PL XVI, Fig. 15), instead of being 

 trilateral as in the corresponding tooth (PL XVI, Figs. 9, 10, a)- of M. Jeffersonii. 

 Its long or transverse diameter measures ten lines, while its short or antero-poste- 

 rior diameter is at the widest part five lines. The lower part of the tooth is broken 

 away ; and the bottom of the pulp cavity is ten lines from the triturating surface, 

 which is worn into a concavity. 



EREPTODOIV, Leidy. 

 Ereptodon priscus, Leidy. 



The collection of Dr. Dickeson contains an isolated tooth, found in a ravine in 

 the neighborhood of Natchez, Mississippi, which has about the same size and struc- 

 ture as the first molar of the Megalonyx Jeffersonii, but has a Very different form. 



In relation to the position of this tooth in the jaw, in comparing it with the 

 teeth of Megalonyx, it would appear to be a first molar, but compared with those of 

 Mylodon, it appears as if it was rather a last inferior molar. 



The specimen (PL XIV, Figs. 9, 10, 11) is an inch and eight lines long, and is 

 excavated from the bottom for the dental pulp, to within seven and a half lines of 

 the triturating surface. The border of the pulp cavity is broken away, and the 

 tooth when perfect has probably been an inch longer. 



In transverse section (PL XVI, Fig. 18), the tooth is elliptical, with a tortuous 

 outline, and the posterior extremity is more obtuse than the anterior. Its long dia- 

 meter is one inch and seven lines ; its short diameter is eight and three-quarter lines. 



The tooth is very slightly curved in its length (PL XIV, Fig. 11), and the tritu- 

 rating surface presents an irregular, antero-posterior concavity. The inner side 



* The figure 13 of Cuvier's plate is reproduced in figure 6, Plate Ixxx, of Owen's Odontography ; 

 and also in figure 1, Plate xvii, of the Zoology of the Voyage of the Beagle, as characteristic of the 

 Megalonyx Jeffersonii. 



