I took this picture on the coast of a lake near the border of NC and SC. This is the shell of an ocean quahog. This photo was taken around 1:00pm.
According to the Mother Nature Network, ocean quahogs have one of the longest life spans – some have been more than 400 years old. (http://www.mnn.com/earth-matters/wilderness-resources/photos/10-animals-with-the-longest-life-spans/ocean-quahog)