We show a surprising connection between known integrable Hamiltonian systems
with quartic potential and the stationary flows of some coupled KdV systems
related to fourth order Lax operators. In particular, we present a connection
between the Hirota-Satsuma coupled KdV system and (a generalisation of) the
1:6:1 integrable case quartic potential. A generalisation of the 1:6:8 case
is similarly related to a different (but gauge related) fourth order Lax
operator. We exploit this connection to derive a Lax representation for each of
these integrable systems. In this context a canonical transformation is derived
through a gauge transformation.Comment: LaTex, 11 page