92 TERTIARY SERIES. 
Tapir of Cuvier), is calculated to have been 
eighteen feet in length, and was much the largest 
of all terrestrial Mammalia yet discovered, ex- 
ceeding even the largest fossil elephant. 
The Dinotherium will be described in a sub- 
sequent chapter. 
Mammalia of the Pliocene Periods. 
The third, and fourth, or Pliocene divisions 
of the tertiary fresh-water deposits, contain no 
more traces of the extinct lacustrine genera of 
the Palseotherian family, but abound in extinct 
species of existing genera of Pachydermata, 
e. g. Elephant, Rhinoceros, Hippopotamus, and 
Horse, together with the extinct genus Mas- 
todon. With these also occur the first abundant 
traces of Ruminantia, e. g. Oxen and Deer. 
The number of Rodentia becomes also enlarged ; 
and the Carnivora assume a numerical import- 
ance commensurate with the increased numbers 
of terrestrial herbivora. 
The seas, also, of the Miocene and Pliocene 
periods, were inhabited by marine Mammalia, 
consisting of Whales, Dolphins, Seals, Walrus, 
and the Lamantin, or Manati, whose existing 
species are chiefly found near the coasts and 
mouths of rivers in the torrid zone (see PL 1, 
Figs. 97 to 101). The presence of the Lamantin 
adds another argument to those which arise from 
