(Chapter 15) Footnote 29:

See De usu partium (4.30.15ff., May pp. 564ff.) where Galen describes the more than twenty muscles that move the head. See also book 4 of De anatomicis administrationibus, and De musculorum dissectione. Of the last two, Galen cites the first by name in De usu partium and mentions the second only as “one other book.” See May p. 566 and notes 36-37.