10 MEMOIR ON THE III. 



All the specimens are from the vicinity of Natchez, Mississippi. Two of them 

 were found by Dr. M. W. Dickeson in association with remains of Mastodon, Equus, 

 Ursus, Cervus, Megalonyx, and Mylodon; the others belong to the American Philo- 

 sophical Society, to which they were presented by W. H. Huntington, Esq., who 

 discovered them in association with remains of Mastodon, Equus Americanus, and 

 the jaw of Felis atrox, described by me in the Transactions of the latter Society. 



Three of the teeth are superior molars ; one, the last of the series (Plate II., 

 Fig. 4), is unworn, the others are moderately so.. The inferior molars are both the 

 last of the series ; and one is unworn, while the other is worn down within half an 

 inch of the fangs, which are elongated, as is ordinarily the case in the teeth of old 

 ruminating animals. 



In the upper molars the external side exhibits six folds relatively not more pro- 

 minent than in the common ox. Internally between the principal lobes, the acces- 

 sory column is very well developed and robust (Figs. 2, 4). The crescentic enamel 

 pits or islands of the grinding surface are more simple than in the ox, and appear 

 relatively more capacious as a result of their greater simplicity or less degree of 

 inversion of the sides of the pits (Fig. 3). 



The last lower molar (Fig. 5) also presents a well-developed accessory column 

 between the anterior pair of principal lobes externally, and in the worn down 

 specimen (Figs. 6, 7), upon the triturating surface forms a correspondingly larger 

 fold. In the unworn specimen, the summit of the posterior lobe bifurcates ante- 

 riorly, one portion joining the postero-internal fold of the middle lobe, the other 

 the postero-external angle of the same lobe. 



Admeasurements of the Teeth. 



Unworn superior last molar : 



Length ......... 36 lines. 



Antero-posterior diameter externally . . . . 20 " 



Transverse diameter at the middle of the tooth anteriorly 14 " 



Transverse diameter at bottom . . . . . 17 " 



Two superior true molars, probably first and second : 



Length 30 and 33 " 



Antero-posterior diameter . . . . . . 18 " 



Transverse at middle . . . . . . . 13 '' 



Unworn inferior last molar : 



Length ... 36 " 



Antero-posterior diameter . . . . . 25 " 



Transverse ... . . . . . 9J " 



Worn inferior last molar : 



Length of crown . 6 " 



Antero-posterior diameter of triturating surface . . 25 " 



This last specimen appears somewhat water-worn and rolled. A portion of the 

 anterior fangs are broken off, and the posterior, which is now fourteen lines long, is 

 partially worn away. 



