Family †Helcionellidae | Order †Helcionelliformes Rank Genus | |
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Mackinnonia is a genus of small shelly fossil comprising straight or slightly coiled shells of the helcionelloid type. The outer surface of their shell is smooth, whereas the inner surface has a net-like ridges. They are known from late Early Cambrian rocks across North America and Greenland.
References
Mackinnonia Wikipedia(Text) CC BY-SA