Select list of table names for particular DB

Hi
I am trying to figure out how to get (select) a list of all the names of
the tables in a database when given the name of the database. ie.,
Select table_name from ??? where datbase name = "XYZ";
I can easily select names of tables in current db like this:
SELECT datname FROM pg_database;

But, if I want to retrieve all table names for a different db, I can
not figure it out.
I looked at doc for pg_class and can find a relation name but no ID#.
I thought maybe I could find a database ID related to table IDs, but
can not determine what a databases classID might be or what a tables
ID might be.

What system catalogs do I need to access for this information?

Thanks
Jeff

Jeff Webb
University of Scranton