Which also applies with Z, as it does with S' as with James' book and not James's book... and Herz' contribution to our hobby and not Herz's contribution to our hobby... but, I think there might be a difference in period (time) as with the "English" language and the "American English" language in the case with S' as in St James's London in proper English... Surely anything named St James's is spelled correctly (St James's Casino).