How can you tell the difference between seals and sea lions?

Sea lions (otarids) can fold their hind quarter underneath themselves when on dry land. They have larger front flippers and use them to propel themselves through the water. They have visible ear flaps.

Seals (phocids) can not bend their back end under themselves and propel themselves on their bellies when on land. They swim primarily with their back legs. They do not have ear flaps.