The grinding teeth (or molars) of beasts are divided into premolars and true molars.

The premolars are molars which have deciduous vertical predecessors (or milk teeth), and any which are in front of such, _i.e._ between such and the canine tooth.

The true molars are those placed behind the molars having deciduous vertical predecessors.

Now, as a dentition becomes more distinctly carnivorous, so the hindmost molars and the foremost premolars disappear.

In the existing cats this process is carried so far that in the upper jaw only one true molar is left on each side.