Many of the oxysulfides containing two metals have layered structures of ( RO) sheets and ( MxSy) sheets ( R = rare earth, M = Cu, Ag, Ga, In, Ge, Sn, As, Sb, Bi). In the new compounds (La 4O 3)(AsS 3) 2 and (La 5O 3)In 6S 17, parallel ribbons of stoichiometry (La 4O 3) and (La 5O 3) substitute for the (LaO) sheets. The formation of ribbons is explained by shear mechanisms involving two different orientations of the periodic shear planes in the tetragonal (LaO) sheet. In a third compound La 3GaS 5O or (La 2O)LaGaS 5, the formation of (La 2O) ribbons involves similar shear mechanism. All these shear structures preserve the main characters of the layered oxysulfides: oxygen is only bound to lanthanum, and the second metal is only bound to sulfur.