These pictures are not of fossils but of a modern day bivalve. It is a cross-hatched lucine (Divaricella quadrisulcata Orbigny 1842). I am posting it because of the unique pattern of its shell. It reminds me of a Waldron Shale brachiopod fossil Dictyonella reticulata not that they have similar patterns but that they have such distinct patterns. Once you see a shell like this, you know what it is because of its unique pattern.
This shell was found on Folly Beach South Carolina USA in August 2017. See this site for help with shell identifications:
https://www.mitchellspublications.com/guides/shells/articles/pictorial/
