\fbox{
\begin{tabular}{cl}
  \multicolumn{2}{c}{Mutations} \\ \midrule
  \raisebox{-0.15ex}{\includegraphics*[scale=0.75,viewport=130 55 177 61]{appendix_files/legend-width2.pdf}}
  & width 2\\
  \raisebox{-0.15ex}{\includegraphics*[scale=0.75,viewport=130 55 177 61]{appendix_files/legend-width3.pdf}}
  & width 3\\  
  \raisebox{-0.15ex}{\includegraphics*[scale=0.75,viewport=130 55 177 61]{appendix_files/legend-width4.pdf}}
  & width 4\\  
  \raisebox{-0.15ex}{\includegraphics*[scale=0.75,viewport=130 55 177 61]{appendix_files/legend-width5.pdf}}
  & width 5\\  
  \raisebox{-0.15ex}{\includegraphics*[scale=0.75,viewport=130 55 177 61]{appendix_files/legend-widthbig.pdf}}
  & width ${6+}$\\  
\end{tabular}
}
