Removing bulbs from side marker lights?

70 Dart, front marker lights (orange ones). I can't for the life of me figure out how to remove the sockets to change the bulbs. The housings are pretty dirty, being in the wheelwell and all, but do you just pull? Or twist so they unlock? I can't get it to twist but I looked at another set of housings I have and there doesn't appear to be anything to lock into?