The top photo is of a Fixed Crinoid. The stem is plainly visible. The cups located at the top part of the stem were known as the aboral cup. Arms would grow up from these cups- in the photo at the top you can see the indentions for at least two of these arms. See http://www.fossils-facts-and-finds.com/crinoid.html for an drawing of the completed plant.
The middle photo is of a Feather Star crinoid. I found it in a rock along the river bank as well. This is the only one of these that I have ever found.
The last photo shows a crinoid stem section. This is the most common fossil type found here in North Alabama.
Since I was a kid, I enjoyed finding these fossils. There was and is something cool to me about finding a fossil. Unfortunately, I never knew what type of fossil that I was finding. The kind of fossil that I found most often were the round fossils (usually about the size of a dime) with a hole in the middle. I have since discovered that these fossils were a small part of a organism known as a Crinoid that lived in the Ordovician period a long time ago (scientists estimate 542 to 488 million years ago). Thanks to paleophilospher for his comment regarding the period in which the Crinoids originally lived.
I have been combing the shore of the Tennessee River in Limestone County for the past few weeks. I have found several nice Crinoid fossils- including two different types of the Crinoids. The two types are the "sea lily" or Fixed Crinoid and the "Feather Star" or Free Swimming Crinoid.