(Chapter 31) Footnote 37:

The margin cites ch. 22 of De ossibus: “These convex, fleshless, and projecting parts are properly but quite mistakenly called astragaloi, for the astragalos is enclosed by these hammers [malleoli], sheltered by them on all sides, and inaccessible.” (2.774.17-775.5, tr. Singer 1952, p. 774).