as 
The number of teeth in each side of each jaw is supposed to be 
six, following in succession, one behind the other. The first one 
has four to six rings or plates ; the second, eight or nine ; the 
third, eleven to thirteen ; the fourth, fifteen or sixteen ; the fifth, 
seventeen to twenty ; and the sixth, twenty-two to twenty-seven. 
In the Mastodon the number is the same, six ; and the compara- 
tive age is recognized by the number of tubercular ridges, and the 
size and form of the crown. The first and second had but two 
ridges, the latter larger in size ; the third in succession had three 
ridges and was narrowed in front ; the fourth had three ridges, 
but was of equal width at the ends ; the fifth had three ridges 
only, was widest behind and with long fangs ; the sixth tooth had 
four ridges and a heel, or imperfect fifth ridge. The comparative 
time the last tooth had been in use is recognized by the degree 
of wearing it has undergone. Teeth representing some of these 
stages in the Mastodon can be seen in Case Q, Sect. 13. 
Fig. 48.— Tooth of Elephas 
Americanus (XX)- 
Fig. 49.— Tooth of Mastodon 
giganteus (XW 
UNGUICULATES. {Clawed Animals.) 
This group includes the Carnivores or flesh-eaters, and is divided 
into Creodonta, ancient carnivores, and Carnivora, living 
carnivores. 
The Creodonts all belonged to the lower Eocene period. They 
are represented in the large case by teeth and jaws of two spec.es 
of Pachyana. One of these, P. gigantea, is the largest known form 
of these animals, having been about as long as the Grizzly Bear 
bui with a more slender body. Another form, Palaomctis, was 
