We report the synthesis and structural characterization of a new homologous series of lanthanum cuprates, with the formula La4+4nCu8+2nO14+8n. The n = 2 and n = 3 members, La2Cu2O5 and La8Cu7O19, synthesized in the bulk, are stable in very narrow temperature ranges in air and oxygen. The n = 4 member was observed by electron microscopy. The crystal structure of La2Cu2O5 consists of thin ribbons of La2CuO4 sandwiched between CuO planes of complex low dimensional geometry. The temperature-dependent magnetic susceptibilities of La2Cu2O5 and La8Cu7O19 are characteristic of low dimensional Heisenberg antiferromagnets with a low exchange coupling energy.