I construct classical superextensions of the Virasoro algebra by employing
the Ward identities of a linearly realized subalgebra. For the N=4
superconformal algebra, this subalgebra is generated by the N=2U(1)
supercurrent and a spin~0 N=2 superfield. I show that this structure can be
extended to an N=4 super W3 algebra, and give the complete form of this
algebra.Comment: 15 pages, USC/92-02