It is also commonly preserved as an internal mold, which does not show the selenizone. This genus is restricted to the Upper Ordovician. The gastropods are a quite a diverse group as described before. The two specimens collected here, Liospira vitruvia and Clathrospira subconica , are both from Order Archaeogastropoda. Both are herbivores and are preserved by internal mold.
Gastropods are relatively tough to distinguish due to their mode of preservation.
Many are internal molds, which are useful, but others are external molds, and they do not give much hints to the age of the gastropod. Cyclonema , also an archeogastropod, is Ordovician in age and preserved here as original shell. This is a chaetetid from southeastern Indiana. It is Ordovician in age, and the calcitic replacement mechanism is unknown. Chaetetids are a very strange group of sponges.