Spinotrapezius, also called thoracic trapezius, is the most posterior of the three trapezius muscles. It is triangular shaped. Posterior to the acromiotrapezius and overlaps latissimus dorsi on the front. Its origin is the neural spines of the thoracic vertebrae and its insertion is the scapular fascia. Its action is to draw the scapula to the dorsal and caudal regions. [ http://en.wikipedia.org/wiki/Cat_anatomy#Spinotrapezius ]