I'm going to concur with TonySi..... the common Atlantic sea star,
Asterias rubens. These are very common stars, whose habitat ranges from the shallow reef waters along the southern coasts to pale colored deep- and coldwater varieties up the northern atlantic coastline. They are considered opportunistic predators, and often feed on bivalves found in the substrate of the seabed, such as clams and mussels. I have no idea if they are coral safe (a cursory internet search didn't reveal much on the subject), but I would think 3 or 4 times about putting any wild-caught star in my tank.
Yes, I know you were just looking for the basic info and you don't have a tank - I was just saying that for the benefit of others.