adding ticks to the contMap plot legend, or a way to discretize by range

I've searched a lot and couldn't find a way to do that. I was wondering if it's possible to add ticks to the legend bar produced by `contMap`. Sometimes it's nice to know the values assigned to certain colors. That led me to the next question, is there a way to discretize it, and break the bar in into solid colors for certain parts of the range?
