Beef Ribs?

My wife bought some beef ribs for me to smoke this past weekend. I know next to nothing about beef ribs, but these were really cheap. They looked like pork spare ribs, just alot larger. I smoked them for 4 hours at 230ish and cut one rib off to try. It was a little tough, so I left them on for another hour. Much more tender, but some of it was dry.
My quesion is, how do you tell when they are done? Also, what are the different types of ribs?

Oops.. didnt see that. Did a quick posting before heading to lunch. Thanks!