How do I change gasket on Custom Molded Products PowerClean Chlorinator?

[starkraven]

Greetings, all. I have a Custom Molded Products PowerClean Chlorinator that is leaking from under the top lid. The reddish gasket appeared to be quite degraded, so I ordered another one. The old gasket appears flat and imbedded in a groove in the lid.

Here's my dumb question: should I dig it out the old gasket and put the new gasket there? Or put the new gasket on top of it? While the new gasket is a perfect fit as far as circumference goes, is appears to be a different form. The new gasket is tubular. The old gasket appears flat.

 

[Bama Rambler]

Remove the old one and replace it with the new one.
The old gasket may have been tubular when new and has flattened over time. Or they may have changed the design.