premise: a <mask> synovial membrane; the <mask> process of the temporal bone.
hypothesis: the best context for <mask> here is Of or pertaining to a vagina; resembling a vagina, or sheath; thecal; but not One of a system of ordnance, including machine, quick-fire, coast, and field guns, of all calibers, manufactured by the combined firms of Vickers' Sons of Sheffield and Maxim of Birmingham and elsewhere, England..