  We construct a complete classification of pentaquark states in terms of the
spin-flavour SU(6) representations. We find that only some definite SU(3)
representations are allowed, singlets, octets, decuplets, anti-decuplets,
27-plets and 35-plets. The latter three contain exotic states, which cannot be
constructed from three quarks only. This complete classification scheme is
general and model independent and is useful both for model builders and
experimentalists. The mass spectrum is obtained from a Gursey-Radicati type
mass formula, whose coefficients have been determined previously by a study of
qqq baryons. The ground state pentaquark which is identified with the recently
observed Theta(1540) state, is predicted to be an isosinglet anti-decuplet
state. Its parity depends on the interplay between the spin-flavour and orbital
contributions to the mass operator.
