Strange find

[reh76]

Ran over to the beach Saturday to look for shark teeth. My 5 year old son found these 2 nice pieces. We found a good spot that looked freshly eroded, turned out to be ripe. Plenty of teeth, bone fragments, stingray barbs and snail shells. The strange find was this rock, anybody know what it is? My first thought was it was one of those created by lighting hitting the sand, but I really don't know. Any guesses?