MAMMALIAN FOSSILS FROM DEVIL'S GULCH 179 



cordingly, the anterior cones and plates of mastodons and mam- 

 moths are ground in front long before they are worn behind. 



The mandibular teeth of mastodons are ground most in front, 

 and generally with an outward slant. This gives a clue to the 

 orientation of odd mastodon teeth. The mandibular teeth of 

 mammoths are roughly crescentic, the ground or worn surfaces 

 are upward and forward, and the convexity inward, which enables 

 one to orient and locate a given tooth. The maxillary teeth of 

 mammoths are generally massive, the grinding surface is down- 

 ward, and the greater convexity of surface outward. 



Though the more advanced and specialized proboscideans have 

 the number of grinding teeth reduced to one or two, they may have 

 had, at some earlier stage in their life, four or five in use at once. 

 This points to an ancestry with many grinders. The short- 

 crowned (brachydont) teeth, with but three, four, or five trans- 

 verse ridges, changed to the tall-crowned (hypsodont) teeth with 

 ever-increasing transverse ridges found among the intermediate 

 and true elephants. Increase in number of ridges signifies ad- 

 vancement. The earlier mastodons had 3 transverse ridges, later 

 mastodons 4 or 5. The intermediate elephants, Stegodonts, had 6 

 to 12, and the mammoths and modern elephants 16 to 24, and even 

 28. Along with the multiplication of transverse ridges went the 

 increase in cement reinforcement signifying specialization. 



THE TUSKS 



Morphologically, tusks are incisors which grow from persistent 

 pulps. A series of fossil proboscideans show that the tusks gradu- 

 ally lengthened, and increased in weight, during the ages, until 

 they became ponderous. Great muscles and sinews were neces- 

 sary to support the weight of the ever-lengthening tusks and trunk. 

 Accordingly, insensible changes took place. The early dolico- 

 cephalic skull, and longirostral jaw changed to the brachycephalic 

 and brevirostral. 



Early mastodons had short decurved tusks with enamel bands. 

 Intermediate mastodons had longer and larger tusks with vestigial 

 enamel bands, while later ones had long, straight, or slightly spiral 

 tusks with the enamel band wanting. Though mastodon tusks are 



