The nasal bones are often ossified together to form one bone. The surface of the skull is in general oval and smooth, but in some of the Baboons there appear strong ridges over the eyes (hiding the forehead) and along the top of the head, being stronger, when present, in the male than in the female. The external orifice to the ear has a considerable bony tube, or meatus, a distinguishing character which is absent in the New { 251}World Monkeys; their tympanic (or ear) cavity being close to the outer wall of the skull. The line of junction (or suture) between the upper jaw-bones, the pre-maxillary and the maxillary, remains unclosed until long after the permanent teeth have come in. Sometimes it remains unclosed throughout life. The foramen for the passage of the spinal-cord, and the condyles for the articulation of the skull with the neck, lie far back.
In the spinal column there are nineteen dorsal and lumbar vertebræ together. The number of caudal vertebræ varies greatly; in some there are as many as thirty-one, in others only three. The posterior ends of the ischiatic bones of the pelvis are rough, flattened, and broad, for the attachment of the fleshy callosities mentioned above.
The bones of the thigh and leg (_femur_ and _tibia_) together, are longer than those of the arm and fore-arm (_humerus_ and _radius_) together. The bones of the thumb are modified more for support and progression than for the actions of a true hand; by these modifications the movements of rotation (pronation and supination) are much restricted.
The ankle (_tarsus_) does not exceed one third of the length of the foot.
The stomach is simple, or but very slightly sacculated, in those genera which possess cheek-pouches; but is tripartite--the middle compartment being sacculated--in those that have not store-pockets in their mouths, "a groove with raised edges leading from the gullet-entrance to this middle compartment." The intestine has a cæcum, or blind diverticulum. "When laryngeal air-sacs are developed, they are formed by a single sac, with a median aperture--immediately beneath the epiglottis. This median air-sac is very large, extending down { 252}over the front of the neck, and sending [in some genera] processes into the _axillæ_" or arm-pits. (_Huxley._)