This is the urinal in the little bathroom booth at the top of the hill. They're the waterless no-flush variety. This fixture is not located inside the prison complex itself.
This trough is located adjacent to the boat dock where visitors can board the ferry back to San Francisco. These first two photos were taken by Urinal Dot Net staff in 2000.
This latest photo was taken by AB in 2012 in what used to be the communal shower room at Alcatraz (now used as a guest men's room adjacent to the entrance)