archaeogastropod

*Archaeogastropoda* (also known as *Aspidobranchia*) was a taxonomic order of sea snails used in older classifications of gastropods, i.e. snails and slugs. *Archeogastropoda* are marine prosobranch gastropod mollusks, mainly mainly herbivores, typically having two gills and a double-chambered heart, with the eggs and sperm discharged directly into the water. They were traditionally regarded as a relatively primitive group. [https://en.wikipedia.org/wiki/Archaeogastropoda]