CHAPTER XV
HISTORY OF THE PRIMATES
This order embraces the lemurs, monkeys, man-like apes and Man, though in the general account Man will be omitted from consideration. The Primates are clothed in dense fur or shaggy hair. The teeth are always low-crowned and rooted and reduced in number, the incisors generally to 2/2 and the premolars to 3/3-2/2; the molars are trituberculate or quadrituberculate. The cranium is unusually capacious and the orbit is entirely encircled in bone. The tail varies much in length and may be entirely wanting. The bones of the fore-arm and lower leg are separate and the radius has much freedom of rotation, in correspondence with the grasping power of the hand. The pes is also a grasping organ and, with few exceptions, the thumb and great toe are opposable to the other digits; the bones of the wrist do not coössify and frequently the central is present. The feet are plantigrade and almost always pentadactyl and, with a few exceptions, have neither claws nor hoofs, but flat nails; the ungual phalanges are correspondingly modified and do not taper toward the free end, but expand at the tip. The Primates are characteristically arboreal in habit, but a few, such as the baboons, have become secondarily adapted to a terrestrial mode of life. They inhabit at present all the tropical regions of both hemispheres, Australia excepted. Extra-tropical North America has no existing member of the order and, so far as we know, has had none since the Eocene epoch. The most important of the genera of the western hemisphere are listed below.
Suborder LEMUROIDEA. Lemurs
I. †Notharctidæ.
†Pelycodus, low. and mid. Eoc. †Notharctus, Eoc.
II. †Anaptomorphidæ.
†Anaptomorphus, low. and mid. Eoc. †Omomys, mid. Eoc. †Hemiacodon, do.
Suborder ANTHROPOIDEA. Monkeys, Apes, Man