(Chapter 21) Footnote 43:

That is, the acromion. The confusion perhaps arises not from inconsistency in Galen but from an error in the transmitted text. Kühn’s e)/cwqen de\ “on the outside” was amended by Helmreich to e)/swqe/n te, “on the inside.” See May 1968 p. 614 n. 54. In that passage (on which see n. 27 above) Galen’s identification of the acromion as the coracoid adds to the confusion.