The purpose of this paper is to classify torus manifolds (M 2n , T n ) with codimension one extended G-actions (M 2n , G) up to essential isomorphism, where G is a compact, connected Lie group whose maximal torus is T n . For technical reasons, we do not assume torus manifolds are orientable. We prove that there are seven types of such manifolds. As a corollary, if a nonsingular toric variety or a quasitoric manifold has a codimension one extended action then such manifold is a complex projective bundle over a product of complex projective spaces.

The purpose of this paper is to study relations among equivariant operations on 3-dimensional small covers. The author gets three formulas for these operations. As an application, the Nishimura's theorem on the construction of oriented 3-dimensional small covers and the Lü-Yu's theorem on the construction of all 3-dimensional small covers are improved. Moreover, for a construction of 3-dimensional 2-torus manifolds, it is shown that all operations can be obtained by using the equivariant surgeries.