Activity

probably the inner mould of a turritella snail shell?

Possibly

That makes sense or something similar

There are a few fossils to the left of it and above main segment.

The others are other gastropods

http://www.uky.edu/OtherOrgs/KPS/images/archimedes.jpg

Bryozoa (Moss animals)
Bryozoans (sometimes referred to as Entoprocta and Ectoprocta) are microscopic sea animals that live in colonial structures that are much larger than the individual animal. Because these structures are usually composed of secreted calcite, they commonly form fossils. Bryozoans were so common in Kentucky’s ancient past that they may be the most common form of fossil found in the State.

Bryozoan fossils occur in many forms, including finger-shaped, fan-shaped, mats, spiralling fans, and massive irregular mounds. Many of the fossils, if examined closely with a magnifying glass, will show the individual pits where the individual bryozoans lived. Each animal was attached to the inside of its pit and could not leave the pit. Bryozoa feed on microscopic organisms floating in the water, which they grab with tiny tentacles. Bryozoan fossils can be found in Kentucky’s Ordovician, Silurian, Devonian, Mississippian, and Pennsylvanian rocks.