TRANSACTIONS OF WAGNER 



MASTODON 



Commonly in the description of the molar teeth of Mastodon they seem 

 to be viewed as rather being of a perissodactyl than an artiodactyl character, 

 the constituent pairs of lobes of the crown being described as cross ridges or 

 crests. Professor Owen speaks of the Mastodon as being at the Tapiroid or 

 Dinotherian extremity of the Proboscidian series, manifested by modifications 

 of the teeth most meriting to be held generically distinct from those of exist- 

 ing Elephants, the grinding surface of the molars instead of being cleft with 

 numerous plates is divided into wedge-shaped transverse ridges, and the sum- 

 mits of these are divided into smaller cones, more or less resembling the teats 

 of a cow, whence the generic name. The molars of Mastodon, in structure, 

 bear more resemblance to those of a Hippopotamus than to those of a Tapir 

 or Dinotherium. The crown exhibits a distinctly paired lobular constitution, 

 as in the artiodactyla generally. According to the usual plan in the latter, 

 the upper and lower teeth are similarlj' related. 



The molars of the common American Mastodon, M. americanus, whose 

 remains are so widely distributed through North America, exemplify among 

 the many recognized species the simplest constitution. Selecting as types the 

 intermediate molars of the series, the crown is composed of three successive 

 pairs of pyramidal lobes, separated by deep angular valleys and embraced by 

 a basal ridge. The lobes of each pair are extended and conjoined by a medial 

 offset variably distinct, longer and wider in the outer lobes of the upper molars 

 and inner lobes of the lower molars. Together at the summit they form an 

 acute, tubercular ridge or crest, with a wide notch ending in a median vertical 

 cleft, which defines the inner from the outer lobes. The inner lobes of the 

 upper and the outer lobes of the lower molars are wider at base than the 

 others, are more inclined laterally, and are proportionately narrower at the 

 summit. Medially in front and behind they present a conspicuous ridge or 

 buttress, extending from the summit to the base of the lobes. In the valleys 

 the contiguous buttresses conjoin, producing a slight obstruction in their 

 course, and at the front and back of the crown they end in or unite with the 

 contiguous basal ridge. In the outer lobes of the upper and inner lobes of 



true molars. The first and second milk molars and the later premolars have the crown composed of 

 two pairs of lobes, while all the others except the last ones have three pairs of lobes. 



II. von Meyer, in the Palsontographica, 1870, represents the molar dentition of the same species 

 as consisting of the same kinds and number of teeth, but regards the later premolars as vertically 

 succeeding the anterior two deciduous molars, to the first of which he ascribes two pairs of lobes to 

 the crown, while to the second, as well as the third, he ascribes three pairs of lobes. 



