146 _ BIRD GALLERY. 
as the uncinate processes (fig. 011 & fig. 71). These are flat blade- 
shaped bones attached to the middle of one rib and sliding over the 
outer surface of that immediately behind it. 
The breast-bone or sternum (fig. 512) is a large, broad, more or less 
convex bone which protects not only the thorax, but also a part of the 
abdomen. In all birds in which the fore-limbs act as the principal 
organs of locomotion, this breast-bone is provided with a deep crest 
or keel (13) for the attachment of the muscles of flight. In proportion 
as the power of flight is diminished, this crest becomes less prominent 
and may disappear altogether. 
The pectoral arch or shoulder-girdle consists of three pairs of bones— 
the pillar-like coracoids (fig. 5 14), the scapulze or shoulder-blades (15), 
which are narrow and sabre-shaped, and the clavicles or collar-bones 
(16), which are generally united at their lower end and form a 
V-shaped bone, the furcula, commonly known as the “ merry-thought.” 
The principal support of the attachment of the wing to the trunk is the 
coracoid, which is broadly joined to the anterior extremity of the 
sternum and forms, together with the scapula, the base of attachment 
for the humerus or upper arm-bone. ‘The fore-limb consists of the 
following parts:—the upper arm-bone (humerus) (17), forearm (ulna 
and radius) (18, 19), two small free wrist-bones (20, 21) (carpals), an 
elongate hand (carpo-metacarpus) (22), and three fingers (digits). Of 
the latter, the thumb ( pollez) (23) is a single stylhform bone joined to the 
first metacarpal and bearing the so-called “ bastard-wing” (fig. 28) ; 
the second or index-finger (24) is the longest, composed of two or 
three joints, and forms the extremity of the wing, while of the third 
(25) there is only a vestige. The thumb and index digit are sometimes 
furnished with a claw. 
The pelvis of Birds is open in front, a union or symphysis of the 
pubic houes (26) occurring only im the Ostriches. The shape of the 
pelvis is remarkable from the great forward prolongation of the iliae 
bones (27), which may extend forwards on to the ribs. The acetabulum 
or socket for the articulation of the hind hmb occupies a position about 
half way between the extremities of the pelvis; the centre of the cavity 
is unossified and appears as a round perforation. 
The hind limb consists of the following parts :—the thigh-bone 
(femur) (29); lower leg (composed of the united ¢2bza and fibula (30, 31), to 
which are fused the proximal elements of the ankle or ¢arsws) ; the foot 
(tarso-metatarsus (32), composed of the distal elements of the tarsus 
fused with the metatarsus and forming a long bone, generally though 
incorrectly called the leg) ; and normally four toes (digits). The most 
characteristic bone of the leg is the tarso-metatarsus, which terminates 
in three articular heads for the attachment of the three front toes in the 
