  A Catalan magma is a unique factorisation normed magma with only one
irreducible element. The \val partitions the base set into subsets enumerated
by Catalan numbers. The primary theorem characterises the conditions which a
set a with product map must satisfy in order to be a free magma generated by
the irreducible elements. This theorem can be used to prove a set of objects
(with a product map) is a Catalan magma. The isomorphism between Catalan magmas
gives a "universal" bijection -- essentially one bijection algorithm for all
pairs of families. The morphism property ensures the bijection is recursive.
The universal bijection allows us to give some rigour to the idea of an
"embedding" bijection between Catalan objects which, in many cases, shows how
to embed an element of one Catalan family into one of a different family.
Multiplication on the right (respectively left) by the generator gives rise to
the right (respectively left) Narayana statistic. The statistic is invariant
under the universal bijection and hence allows us to determine what structures
of any Catalan family are associated with this refinement. We discuss the
relation between the symbolic method for Catalan families and the magma
structure on the base set defined by the symbolic method. This shows which
"atomic" elements are also irreducible. The appendix gives the magma structure
for 14 Catalan families.
