  The Machian cosmological solution satisfying $\phi =O(\rho /\omega)$ in the
generalized scalar-tensor theory of gravitation with the varying cosmological
constant is summarized. The scalar field $\phi $ with the exponential potential
is introduced as dark matter and the barotropic evolution of matter in the
universe is discussed. As the universe expands, the coefficient $\gamma $ of
the equation of state approaches to -1/3 and the coupling function $\omega
(\phi)$ diverges to $-\infty $.
