In higher vertebrates ossification sets up in the cartilage and gives rise on each side to a dorsal bone, the =scapula=, and frequently to an anterior ventral bone, the =precoracoid=, and a posterior ventral bone, the =coracoid=. The precoracoid is often not ossified, and upon it is developed the clavicle which more or less replaces it. In some forms a =T= shaped _interclavicle_ occurs, in others =epicoracoids= are found in front of the coracoids. In all vertebrata above fish, except the great majority of mammals, the coracoids are large and articulate with the sternum. But in mammals the coracoids are nearly always quite vestigial, and the pectoral girdle is attached to the axial skeleton by the clavicle or sometimes by muscles and ligaments only. The =Pelvic girdle=[12] like the pectoral consists primitively of a simple rod or hoop of cartilage, which in vertebrata above fishes is divided into dorsal and ventral portions, by a cavity, the =acetabulum=, with which the posterior limb articulates. In the pelvic girdle as in the pectoral one dorsal, and (commonly) two ventral ossifications take place. The dorsal bone is the =ilium= and corresponds to the scapula. The posterior ventral bone is the =ischium= corresponding to the coracoid. The anterior ventral bone is the =pubis= and is generally compared to the precoracoid, but in some cases a fourth pelvic element, the =acetabular= or =cotyloid= bone is found, and this may correspond to the precoracoid. The pelvic girdle differs from the pectoral in the fact that the dorsal bones--the ilia--are nearly always firmly united to transverse processes of the sacral vertebrae, by means of rudimentary ribs. The pubes and ischia generally meet in ventral symphyses. 2. THE LIMBS. It will be most convenient to defer a discussion of the limbs of fishes to chap. VIII. All vertebrates above fishes have the limbs divisible into three main segments:-- =Anterior or Fore limb.= =Posterior or Hind limb.= Proximal segment. upper arm or _brachium_. thigh. Middle segment. fore-arm or _antibrachium_. shin or _crus_. Distal segment. _manus_. _pes_. The proximal segments each contain one bone, the =humerus= in the case of the upper arm, and the =femur= in the case of the thigh. The middle segments each contain two bones, the =radius= and =ulna= in the case of the fore-arm, and the =tibia= and =fibula= in the case of the shin. * * * * * The manus and pes are further subdivided into (_a_) two or three proximal rows of bones forming the wrist or =carpus= in the case of the manus, and the ankle or =tarsus= in the case of the pes. (_b_) a middle row called respectively the =metacarpus= and =metatarsus=. (_c_) a number of distal bones called the =phalanges= which form the skeleton of the fingers and toes, or =digits=.