for the standard screw on filter, correct above, but for some racing, custom type filters, like the Canton Mecca, it is the other way. It is the "antidrainback" valve under the circle of small inlet holes that keeps the
oil from back flowing to the motor, if mounted in reverse. This "valve" is usually a nytrile or other material large gasket, you can see it under the small holes.
here is what it usually looks like:
http://www.wixfilters.com/productinformation/index.html
hal