based on the painting
...that Shelley's poem On the Medusa by Leonardo da Vinci in the Florentine Gallery is based on the painting which was not in fact authored by Leonardo?
...that <a href="./Percy_Bysshe_Shelley" id="mwArQ" rel="mw:WikiLink" title="Percy Bysshe Shelley">Shelley</a>'s poem <i id="mwArU">On the <a href="./Medusa" id="mwArY" rel="mw:WikiLink" title="Medusa">Medusa</a> by Leonardo da Vinci in the <a href="./Uffizi" id="mwArc" rel="mw:WikiLink" title="Uffizi">Florentine Gallery</a></i> is <b id="mwArg"><a class="mw-redirect" href="./Medusa_(Leonardo_da_Vinci)" id="mwArk" rel="mw:WikiLink" title="Medusa (Leonardo da Vinci)">based on the painting</a></b> which was not in fact authored by <a class="mw-disambig" href="./Leonardo" id="mwAro" rel="mw:WikiLink" title="Leonardo">Leonardo</a>?