Calling generic children from their parent?

[rcollinson@aol.com (RCollinson)]

Problem:
I need to use a type in a generic parent body that is located in the generic
child specification.  I am having problems instantiating the child in the
parent's body.  The type is not recognized unless it is instantiated.  Any
ideas?

generic
type A;
type B;
package foo is
  type My_Type is tagged private;
  procedure Do_This;
  procedure Do_That;
...
  private
  type My_Type is
  record
...
  end record;
end foo;

with foo.bar;
package body foo is
  My_Var : Foo.Bar.My_Extended_Type;  -- !!! How do I get an instance of this
variable
                                                             -- !!! that is a
type from the generic child???
                                                             -- !!! Is this
possible???
end foo;
-- ********************************************************8
generic
package foo.bar is
   type My_Extended_Type is new My_Type with
   record
...
   end record;
...
end foo.bar;