[ODE] How to add a space to a space?

[David Jung]

Hi all.
I'm just implementing some code using the new heirarchical
collision space feature.
It looks like from the manual and API that a space is a
special sort of geom.  (i.e. there exists dGeomIsSpace(geomID) ).
That would lead me to believe that I could add a space-type geom
to a space - thus building a tree of spaced with normal geoms
at the leaves.
However, the only function to add geoms to a space is
dSpaceAdd(dSpaceID,dGeomID), which takes a dGeomID.
According to gcc, a dSpaceID isn't convertable to a dGeomID, so
how to I add a space to an existing space?
Perhaps there should be a dSpaceGetGeomID() function or something?
Thanks for any help.
Cheers,
-David.