Great auricular nerve

It is the largest of the ascending branches of the cervical plexus. It arises from the second and third cervical nerves, winds around the posterior border of the sternocleidomastoideus, and, after perforating the deep fascia, ascends upon that muscle beneath the platysma to the parotid gland, where it divides into an anterior and a posterior branch.

• The anterior branch (ramus anterior; facial branch) is distributed to the skin of the face over the parotid gland, and communicates in the substance of the gland with the facial nerve.
• The posterior branch (ramus posterior; mastoid branch) supplies the skin over the mastoid process and on the back of the auricula, except at its upper part; a filament pierces the auricula to reach its lateral surface, where it is distributed to the lobule and lower part of the concha. The posterior branch communicates with the smaller occipital, the auricular branch of the vagus, and the posterior auricular branch of the facial.

• 
  Dermatome distribution of the trigeminal nerve, also showing the sensory distribution of the great auricular, lesser occipital, and greater occipital nerves.
• 
  Side of neck, showing chief surface markings.

This article incorporates text in the public domain from page 926 of the 20th edition of Gray's Anatomy (1918)

• Diagram at aapmr.org
• Anatomy figure: 25:03-03 at Human Anatomy Online, SUNY Downstate Medical Center - "Diagram of the cervical plexus."