FREE INSTITUTE OF SCIENCE 



MASTODON 



The measurements of the complete specimen are as follows : 



Diameter of the crown fore and aft . . . . 205 mm. 



Diameter of the crown transversely at the anterior lobes . 107 " 



Diameter of the crown transversely at the second lobes . 104 " 



Diameter of the crown transversely at the third lobes . . 99 " 



Diameter of the crown transversely at the fourth lobes . 94 " 



Height of the first inner lobe . . . . . . 85 " 



Height of the second inner lobe .. . . . . 87 " 



Height of the third inner lobe . . . . . . 82 " 



Height of the fourth inner lobe . . . . . . 70 " 



Accompanying the teeth last described, and perhaps belonging to the 

 same animal, is a portion of the crown of a lower right second molar, repre- 

 sented in plate iii. fig. 5. It consists of the posterior two pairs of constituent 

 lobes with the talon. The lobes are worn at their summits, and the forward 

 pair exhibit considerable exposed dentinal tracts, of which the larger outer 

 one is quadrilobate, the inner transversely pyriform. The lobes accord with 

 their homologues of the corresponding upper tooth, but the last outer one 

 has its posterior buttress better developed than in its homologue. The talon 

 is much larger, and consists of a conspicuous pair of conical eminences, of 

 which the "outer is the larger, and by an offset conjoins the buttress of the 

 lobe in advance. The crown as usual is narrower than that of the upper 

 tooth, and like it has considerable cementum. The transverse diameter of 

 the crown at the posterior lobes is 79 mm. 



Two isolated specimens of teeth in the collection are the fifth upper 

 molars, apparently from the same individual. They are both imperfect, but so 

 far as they are preserved they nearly accord in size and other respects with 

 the corresponding teeth above described. The more complete tooth displays 

 all the constituent lobes of its crown, worn to such an extent as to have 

 dentinal areas exposed upon their summits. On the first and second inner 

 lobes the exposed dentinal areas are shield-shape and conspicuously quadrilo- 

 bate. The contiguous outer lobes exhibit transverse elliptical areas. The 

 third inner lobe shows a narrow elliptical islet, extending from the summit of 

 the former along its anterior buttress. The contiguous outer lobe, the least 

 worn, shows a transverse row of three small dentinal islets. In this tooth the 

 posterior buttress of the last inner lobe is more developed than usual. The 

 fore and aft measurement of the crown is 130 mm.; the transverse diameter 

 of the fore part of the other specimen is 88 mm. 



