TRANSACTIONS OF WAGNER 



MASTODON 



Plate iv. fig. 8 represents a first upper premolar of the left side, scarcely 

 worn. The crown is fore and aft oval in outline, and is of much greater 

 transverse width than that of the lower tooth. It also exhibits four con- 

 stituent lobes, with a strong basal ridge. Of the anterior pair, the outer 

 lobe is much the larger and most prominent, is conical, and is partially 

 divided in front, but more behind, and feebly at the summit into two sub- 

 lobes. At the base, in front of the lateral sublobe, is a strong tubercle 

 springing from the basal ridge. The contiguous inner lobe is continous in 

 front, with a stout tubercular ridge curving outward to the tubercle at the 

 base of the outer lobe. The posterior pair of lobes, smaller than anterior, 

 are nearly equal, and widely separated, but conjoined by a small tubercular 

 offset from each. A stout tubercular heel occupies the back of the crown 

 intermediate to the adjacent lobes. A tubercular process of the basal ridge 

 also occupies the outer part of the crown, both in front and behind the first 

 outer lobe, or principal one of the tooth. Another tubercle, at the inner side 

 of the crown, is placed in advance of the posterior lobe, and by an offset 

 joins the anterior lobe. 



The tooth appears to have been invested by a pair of fore and aft connate 

 fangs, of which the posterior was much the stouter. 



The measurements of the tooth are as follows : 



Fore and aft diameter of the crown ... -33 mm - 



Transverse diameter of the crown . . 27 " 



Depth at the principal or first outer lobe . . . . 19 " 



Plate iii. fig. 2 represents the triturating surface of a lower first true 

 molar of the left side, and plate iii. fig. I represents an outer view of the 

 corresponding tooth of the right side in a fragment of the jaw, both from the 

 same individual. These teeth nearly accord in character with the back molars, 

 the crown being composed of three pairs of lobes of the same kind, with a 

 strong basal ridge. The crown is a little worn, so as to expose small dentinal 

 areas on the summits of the anterior pair of lobes and on the median outer 

 lobe. A minute islet is also exposed on the anterior abutment or sublobe of 

 the first outer lobe. The enamel is worn in an inclined plane on the anterior 

 buttress of the third outer lobe, but not on its summit nor that of the contigu- 

 ous inner lobe. In this tooth the offsets of the lobes are mostly distinctly 

 marked as sublobas. The basal ridge is well produced at the outer part of 

 the crown, and behind it is produced into a medial pair of conspicuous conical 



