Even the comparatively scanty Eocene fauna yields examples of the orders Cheiroptera, Insectivora, Rodentia, and perissodactyla; of Artiodactyla under both the Ruminant and the Porcine modifications; of Carnivora, Cetacea, and Marsupialia.
"Critiques and Addresses"
Thomas Henry Huxley
In the perissodactyla the number of toes is reduced to a minimum.
"Natural History of the Mammalia of India and Ceylon"
Robert A. Sterndale