Turritella
Turritella agate is one of the most well-known fossil materials to come out of the Green River formation in Wyoming. It's name is actually a misnomer as the spiral-shaped gastropods do not belong to the Turritella genus of marine snails at all. They are actually Elimia tenera, a freshwater snail and member of the Pleuroceridae family. This is a really fun material and great little fossil specimen for any collection.
