  For some integrable systems, such as the open Toda molecule, the spectral
curve of the Lax representation becomes the graph $C = \{(\lambda,z) \mid z =
A(\lambda)\}$ of a function $A(\lambda)$. Those integrable systems provide an
interesting ``toy model'' of separation of variables. Examples of this type of
integrable systems are presented along with generalizations for which
$A(\lambda)$ lives on a cylinder, a torus or a Riemann surface of higher genus.
