(Chapter 6) Footnote 45:

The membrane “round the skull,” u(mh\n perikra/nioj, is the membrane or periosteum under the skin of the skull. See Galen, De usu partium 3.662.7 and 18 (May, op. cit. p. 412), 690.13, 691.6, 708.7, 748.2, 749.1, 750.18, 922.11.