The bony projection that occurs bilaterally on the posterior aspect at mid-thorax is the of the scapula.

Answer;
Inferior angle
The bony projection that occurs bilaterally on the posterior aspect at mid-thorax is the Inferior angle of the scapula.

Explanation;
Inferior angle of the scapula is where the vertebral and axillary borders intersect. It is located at the lowest part of the scapula and is covered by the latissimus dorsi muscle. It is positioned where the vertebral border, called the medial border, meets the axillary border, called the lateral border.