In this paper, we give a formula for the number of
m-constellations (a family of maps generalizing planar bipartite
maps) having n vertices and p faces. We propose a bijective
proof of our formula based on two main tools, the matching of
Eulerian trees (introduced by Bousquet-Mélou and Schaeffer)
and a correspondence between Lagrangian trees and some
families of endofunctions.