The dynamics of charged particles in x-dependent magnetotail models is examined, where x is along the Sun-Earth direction. An earlier paper showed that particle motion in a class of x-dependent Harris-like equilibrium models can be significantly different from the motion in x-independent magnetotail field models. In the present paper, it is shown that these Harris-like equilibrium models have ''bulb-shaped'' field lines and that this property leads to the reported differences. Furthermore, it is shown that the scale length of variation of the Harris-like models in the x direction, Lx, is comparable to the typical excursion distance, Δ, of particles in the x direction and to &rgr;n which is the gyroradius based on the magnetic field component Bn normal to the plane of the current sheet. It is argued that neither bulb-shaped field lines nor scale lengths Lx comparable to Δ or &rgr;n apply to the Earth's magnetotail. It is suggested that a key criterion for applicability of x-dependent models to the terrestrial magnetotail is Δ, &rgr;n≪Lx. ¿ American Geophysics Union 1993