Scapula

The scapula (or shoulder blade) is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with the scapula on the left side of the body being roughly a mirror image of the right scapula. 

The scapula forms the poster part of the shoulder girdle. It is a flat bone, roughly triangular in shape, placed on the posterolateral aspect of the rib cage.