  Cosmic rays in the energy range $10^{18.0}$ - $10^{18.5}$ eV are thought to
have a light, probably protonic, composition. To study their origin one can
search for anisotropy in their arrival directions. Extragalactic cosmic rays
should be isotropic, but galactic cosmic rays of this type should be seen
mostly along the galactic plane, and there should be a shortage of events
coming from directions near the galactic anticenter. This is due to the fact
that, under the influence of the galactic magnetic field, the transition from
ballistic to diffusive behavior is well advanced, and this qualitative picture
persists over the whole energy range. Guided by models of the galactic magnetic
field that indicate that the enhancement along the galactic plane should have a
standard deviation of about 20$^\circ$ in galactic latitude, and the deficit in
the galactic anticenter direction should have a standard deviation of about
50$^\circ$ in galactic longitude, we use the data of the Telescope Array
surface detector in $10^{18.0}$ to $10^{18.5}$ eV energy range to search for
these effects. The data are isotropic. Neither an enhancement along the
galactic plane nor a deficit in the galactic anticenter direction is found.
Using these data we place an upper limit on the fraction of EeV cosmic rays of
galactic origin at 1.3% at 95% confidence level.
