Clifford algebras of polynomial forms of degree n > 2, introduced by N. Roby are infinite dimensional when the module has rank bigger than I. However, in the case of diagonalizable forms and of binary cubics, we can show that these algebras have finite dimensional quotients. When forms are nondegenerate in a natural sense, these quotients are separable algebras. In the second case, we can also give a precise description of the Clifford algebra itself.