This is a Fossil of a Crinoid Stem from the Mississippian Period and found in Kentucky. This stem has 20 rings. This piece measures approx. 44  x 14 mm: weight is 12 grams.
 
Crinoid Stem The stems of crinoids are a stack of interlocking disks or columnals of a variety of shapes. Often the pillars are arranged in a repeating series of smaller disks.