A biaxial elastic model for the temperature dependence of Sc*helical pitch is proposed on the basis of a phenomenological theory of Sc*liquid crystals accompanied by a biaxial molecular ordering playing an important role for the anomalous behaviour of the helical pitch near the Sc*-SAtransition point. In the Sc*. phase ofp-(n-decyloxybenzylidene)-p-amino-(2-methylbuthyl)-cinnamate (DOBAMBC), a qualitative agreement with the observed helical pitch is found by choosing a few material parameters concerned with a biaxial elasticity and an anisotropy of the elastic constants.