  Kinematics and photometry of the polar ring galaxy NGC 4650A, including new
observations of the rotation and velocity dispersion of its central stellar
disk, are used to infer the presence of a dark matter halo and to measure its
shape. Fits to the observed disk and polar ring rotation curves from detailed
mass and photometric modeling rule out a spherical dark halo. The best fit
models have halos with isodensity surfaces that are flattened to a shape
between E6 and E7 (axis ratios between 0.4 and 0.3); the asymptotic equatorial
speeds of these models are in excellent agreement with the I-band Tully-Fisher
relation. This degree of dark halo flattening is larger than that expected from
N-body collapse simulations of dissipationless dark matter. Since the
kinematics and surface brightness profile of the central luminous body indicate
that its light has an intrinsic axis ratio $c/a \lsim 0.4$, in NGC 4650A the
radial ``conspiracy" between the dark and luminous components that leads to
flat rotation curves may extend to the {\it shape} of the mass distribution as
well.
