The Vestigastropoda is a subclass of gastropods that live only in marine environments and have a nacreous layer. The group includes members of the superfamily Pleurotomarioidea, known for shells featuring a selenizone. The selenizone is a slit feature on shells that the living creature uses to aim its exhalant current.
The Paleozoic gastropod (snail) Shansiella carbonaria (Yin 1932) is a common find in the Pine Creek limestone locality I search in Armstrong County. Specimens are easy to come by, and each is unique and visually pleasing to examine. Norwood & Pratten described this medium-sized snail more than 160 years ago