TRANSACTIONS OF WAGNER 

 2O 



MASTODON 



cessively precede the contiguous outer lobes. As the summits of the inner 

 lobes are worn, the abrasion proceeds from the main eminence to those of the 

 medial offset and buttresses. When much worn, the exposed dentinal surfaces, 

 considerably hollowed, assume a broad, shield-shaped, and mostly a more or 

 less quadrilobate outline. As the summits of the outer lobes are worn, usually 

 two or three islets of dentine first appear, and subsequently, in enlarging, run 

 together, forming a tranversely, in general, elliptical area. 



The lower first and second true and the third deciduous molars are like 

 the corresponding upper teeth, composed on the same pattern. They possess 

 two fangs and have a narrower crown, which is likewise composed of three 

 pairs of similar lobes, but the corresponding ones are reversed in position ; 

 that is to say, the inner lobes are homologous with the outer ones of the upper 

 molars and vice versa. 



The crown of the lower molars is also of less uniform width than in the 

 upper ones, being more narrowed forward. The greater narrowing of the 

 crown seems due to a flattening laterally in the inner lobes and to a less 

 degree of development of their medial offsets than in their homologues, the 

 outer lobes of the upper teeth. The offsets usually form but a single eminence 

 adjacent to the main one at the summit of the inner lobes. 



The talon of the crown is considerably thicker than in the upper molars, 

 and usually supports an unequal pair of conspicuous conical eminences which 

 look like reduced lobes. 



The basal ridge is commonly best developed at the front and along the 

 outer side of the crown. 



Among the most interesting and important remains discovered of M. 

 floridanus are two specimens obtained by Mr. Hatcher in 1890. These con- 

 sist of portions of the opposite sides of the upper jaw of a young animal, 

 both of which contain the third milk molars and the successional premolars. 

 The third milk molar occupies its functional position, and is considerably worn 

 across all the constituent lobes of the crown. The first true molar was par- 

 tially protruded, and is only slightly abraded from use on the summit of the 

 anterior lobes of the crown. The first successional premolar has protruded 

 in advance of the third milk molar, but has barely reached its functional posi- 

 tion. Within the jaw, contained in its appropriate cavity, is the completely 

 developed enamel-cap of the crown of the second successional premolar, 

 situated above and internal to the position of the third milk molar. The teeth 

 appear to have protruded a little irregularly in time on the two sides of the 



