postgres.h location?

I'm looking for the file postgres.h in my recent install of
postgres-7.4.5 on
a MacOS 10.3.5 system.

I'm attempting to build PyGreSQL-3.5, which appears to require the
postgres
include dir.

My build of postgres-7.4.5 did produce an include dir,
/usr/local/pgsql/include;
but it does not contain postgres.h. Curiously, it does contain a file
called postgres_ext.h.
I'm sure they're not one-and-the-same ...

Suggestions?

Thanks in advance!
Scott