  We study theoretically the dynamics of a fluxon Lattice (FL) in two coupled
Josephson junctions. We show that when the velocity of the moving FL exceeds
certain values $(V_{a,b})$, sharp resonances arise in the system which are
related to the excitation of the optical and acoustic collective modes. In the
interval $(V_a, V_b)$ a reconstruction of the FL occurs. We also establish that
one can excite localized nonlinear distortions (dislocations) which may
propagate through the FL and carry an arbitrary magnetic flux.
