Mastodons, like elephants, always have a pair of upper tusks, while the earlier ones likewise have a short pair in the lower jaw, which is prolonged into a snout-like symphysis for their support.
Considering the imprisonment of the ostracod body within the valves, it is more surprising that the Asteropidae and Cypridinidae should have a pair of compound and sometimes large eyes, in addition to the e median organ at the base of I the " frontal tentacle," than 6 that other members of the group should be limited to P that median organ of sight, or have no eyes at all.
In the European Miocene Listriodon, which also occurs in the Indian Tertiaries, the molars have a pair of transverse ridges, like those of the proboscidean Dinotherium; but the genus is believed to be related to the Oligocene Doliochoerus and Choerotherium, in which these teeth show a more normal type of structure.
The opposite or alternate leaves have a pair of small stipules at the base of the stalk and a palminerved blade.
Males have a pair of dagger-shaped horns on the forehead, the tips of which, in some cases at any rate, perforate the hairy skin with which the rest of the horns are covered.
