  Small amplitude inhomogeneous plane waves are studied as they propagate on
the free surface of a predeformed semi-infinite body made of Bell constrained
material. The predeformation corresponds to a finite static pure homogeneous
strain. The surface wave propagates in a principal direction of strain and is
attenuated in another principal direction, orthogonal to the free surface. For
these waves, the secular equation giving the speed of propagation is
established by the method of first integrals. This equation is not the same as
the secular equation for incompressible half-spaces, even though the Bell
constraint and the incompressibility constraint coincide in the isotropic
infinitesimal limit.
