  We have made high-resolution, high-sensitivity dynamic spectra of a sample of
strong pulsars at 430 MHz with the Arecibo radiotelescope. For 4 pulsars we
find faint but sharply delineated features in the secondary spectra. These are
examples of the previously observed ``crisscross'' or ``multiple drift slope''
phenomenon presumed to be due to multiple imaging of the pulsar by the
interstellar medium. The unprecedented resolution and dynamic range of our
observations allow a deeper level of analysis. Distances to the dominant
scattering screen along the line of sight are determined and are shown to agree
well with those inferred from other scintillation phenomena. Multiple imaging
of the pulsar by the ISM is required. A compact central image surrounded by a
faint scattering halo, roughly circularly symmetric, is consistent with the
data. Scattering from filaments may also be consistent. The angular extent of
the scattering material parallel to the direction of the pulsar velocity is
roughly 5 mas, corresponding to a linear extent of about 2 AU. Further
observations of these features should allow better discrimination between
models and an identification of the scattering structures.
