Page 409 - My FlipBook

TEETH OF THE VERTEBRATA. 419
root into two ; (3) addition of basal cnsps from the cingulura. It is a
fact worthy of notice that in the conical dentition the teeth of one series
do not exactly oppose those of the other, but close in the intervals be-
tween them. This in animals that attempted to crush a morsel of food
would cause stimulation of the anterior and posterior edges of the tooth,
thereby determining the point of the greatest nutritive activity and con-
sequent growth. Long-continued vertical pressure I believe to be an
adequate cause for the appearance of the wrinkle or fold of the enamel
covering at the base of the tooth which is designated as the cingulum.

Skull of Mesonyx ossifnigus, anterior to post-glenoid process, one-third natural size, from the Wasatch
beds of Wyoming (after Cope).
The formation of two roots I believe to have been the result of the in-
equality of pressure exerted upon each tooth during the act of mastication,
whereby there was an eifort to displace the tooth in an antero-posterior
direction, or, in other words, to give it a forward and backward rocking