In the CHIROPTERA the scapula is large and oval, and has a moderately high spine and a large acromion. The coracoid process is well developed and is often forked. The clavicles are also well developed, and vestiges of the precoracoid and of the sternal end of the coracoid are often found. In PRIMATES the clavicle and coracoid process are always well developed. In Man and the Gorilla the scapula has a long straight suprascapular border, a well-developed coracoid process and spine, and a large curved acromion. Vestiges of the precoracoid occur at each end of the clavicle. The shape of the scapula varies much in the lower Primates. THE UPPER ARM AND FORE-ARM. In the MONOTREMATA the humerus is short, very broad at each end and contracted in the middle. The radius and ulna are stout and of nearly equal size, while the ulna has a greatly expanded olecranon. In the MARSUPIALIA the humerus is generally a strong bone, broad at the distal end and having well marked deltoid and supinator ridges, which are specially large in _Notoryctes_. An ent-epicondylar or supracondylar foramen (fig. 105, 5) is almost always present except in _Notoryctes_. The radius and ulna are always distinct and well developed, and a certain amount of rotation can take place between them. The ulna of _Notoryctes_ has an enormous hooked olecranon which causes the bone to be nearly twice as long as the radius. [Illustration FIG. 105. ANTERIOR SURFACE OF THE RIGHT HUMERUS OF A WOMBAT (_Phascolomys latifrons_). (After OWEN.) 1. head. 2. greater tuberosity. 3. lesser tuberosity. 4. deltoid ridge. 5. ent-epicondylar (supracondylar) foramen. 6. supinator ridge. 7. external condyle. 8. internal condyle. 9. articular surface for radius. 10. articular surface for ulna.] EDENTATA. The Sloths have long slender arm bones; the humerus is nearly smooth and has a very large ent-epicondylar foramen in _Choloepus_, but not in _Bradypus_. The radius and ulna can be rotated on one another to a considerable extent. The humerus in all other Edentates is very strong and has the points for the attachment of muscles much developed, especially in the Armadillos and Megatheriidae. An ent-epicondylar foramen is found in all living forms. The radius and ulna are well developed, but are not capable of much rotation. In the SIRENIA the humerus is well developed and of a normal character. It is expanded at each end and has a prominent internal condyle, a small olecranon fossa, and no ent-epicondylar foramen. In the Dugong and _Rhytina_ there is a bicipital groove and the tuberosities are distinct, but in the Manatee there is no bicipital groove, and the tuberosities coalesce. The radius and ulna are about equally developed and ankylosed together at both ends.