Search for quark-annihilation type B-meson decays $B^- \to D_S^- \phi$ and B^- \to D_S^{*-} \phi$

We report on searches for $B^- \to D_S^- \phi$ and $B^- \to D_S^{*-} \phi$ based on 230 million $\Upsilon (4S) \rightarrow B\overline B$ decays collected with the BaBar detector at SLAC. The Standard Model branching fractions for these decays are expected to be highly suppressed since they proceed through annhilation of the $b$ and $\bar{u}$ quarks in the $B^-$ meson.