  The action for the D=10 type II Dirichlet super-p-branes, which has been
obtained recently, is reconstructed in a more geometrical form involving
Lorentz harmonic variables. This new (Lorentz-harmonic) formulation possesses
kappa-symmetry in an irreducible form and is used as a basis for applying a
generalized action principle that provides the superfield equations of motion
and clarifies the geometrical nature of the kappa-symmetry of these models. The
case of a Dirichlet super-3-brane is considered in detail.
