A Non-Standard Quark Model and the Mass Difference $\Xi^- - \Xi^0$

We show that a highly unconventional theory, based on the 16 dimensional (${3\over2}$,${3\over2}$) irreducible representation of O(4), fits the masses of the baryons $\Xi^-$,$\Xi^0$,$\Sigma^-$,$\Sigma^0$,$\Sigma^+$,$\Lambda$,$p$,$n$ and the leptons $\mu$,$e$,$\nu_\mu$,$\nu_e$ to within current experimental error, yet yields a prediction substantially different from that of Coleman and Glashow, namely $\Xi^- - \Xi^0 < 6.1$ MeV. We discuss the ramifications of this very non-standard model in the hope to stimulate improved measurements of the $\Xi^- - \Xi^0$ mass difference.