All of the following are contents of the posterior triangle of the neck except:

The posterior triangle is bounded posteriorly by the trapezius muscle, anteriorly by the sternocleidomastoid muscle, and inferiorly by the clavicle.The posterior cervical triangle is subdivided into the following triangles by the inferior belly of the omohyoid muscle:Occipital triangle, whose contents are:Nerve to rhombideusCutaneous branches of cervical plexus of nervesSpinal accessory nerveUpper pa of brachial plexusTransverse cervical aery and veinCervical lymph nodesOccipital aerySupraclavicular nodesSubclan triangle (also known as omoclavicular), whose contents are:Third pa of subclan aeryPa of subclan veinSuprascapular aery and veinSupraclavicular lymph nodesThree trunks of brachial plexusNerve to serratus anteriorNerve to subclaviusSuprascapular nerveLower pa of external jugular veinTransverse cervical aery and vein