Went out to a spot on the Nansemond River in Suffolk, VA, and it started to rain right after. We arrived, so we had to leave. Some iron concretions and this little thing were all I found.
It looks like a clam, but it feels rougher than the other clams I’ve found so far. It was inside of a larger rock. I believe the area is mid-late Pleistocene. It’s about 2 cm wide.