There are two suborders of Chiroptera:
1. The Megachiroptera or Flying foxes, which almost always have smooth crowns to the molar teeth, and the second digit of the manus clawed.
2. The Microchiroptera including all the ordinary bats which have cusped molar teeth, and the second digit of the manus clawless.
Order 9. Primates.
The dentition is diphyodont and heterodont, the incisors generally number 2/2, and the molars, except in the Hapalidae (Marmosets), are 3/3. The cheek teeth are adapted for grinding, and the molars are more complex than the premolars. A process from the jugal meets the postorbital process of the frontal completing the postorbital bar.
The clavicle is well developed, and the radius and ulna are never united. The scaphoid and lunar of the carpus, and commonly also the centrale, remain distinct from one another. As a rule both manus and pes have five digits, but the pollex may be vestigial. The pollex is opposable to the other digits, and so is the hallux except in Man; the digits are almost always provided with flat nails. The humerus has no ent-epicondylar foramen and the femur has no third trochanter.
The order Primates is divisible into two suborders:
Suborder (1). Lemuroidea.
The skull has the orbit communicating freely with the temporal fossa beneath the postorbital bar (except in Tarsius). The lachrymal foramen is external to the margin of the orbit. Both pollex and hallux are well developed. In the pes the second digit is terminated by a long pointed claw, and so is also the third in Tarsius. The lumbar region of the vertebral column is long, sometimes including as many as nine vertebrae. Besides the Lemurs the group includes the aberrant Tarsius and Chiromys.
Suborder (2). Anthropoidea.