  We analyze the existence, stability, and mobility of gap solitons (GSs) in a
periodic photonic structure built into a nonlocal self-defocusing medium.
Counter-intuitively, the GSs are supported even by a highly nonlocal
nonlinearity, which makes the system quasi-linear. Unlike local models, the
variational approximation (VA) predicts the GSs in a good agreement with
numerical findings, due to the suppression of undulating tails of the solitons.
