Florigemma

Jurassic

Phylum: Echinodermata
Class: Echinoidea
Order: Cidaroida
Genus: Cidaris

'Club' shaped
Thorns

Mineral replacement (calcite)
Disarticulated from body shell

This is a spine from a regular echinoid. You can tell this by the shape and thickness of the spine.
Irregular echinoids live under the sediment in burrows, using their spines for movement, not for protection, and hence the spines are fine and able to be manipulated.
Regular echinoids live epifaunally, and so are a target for predators. These spines are needed to prevent attack of the shell containing the soft parts of the animal, and the 'club' like shape decreases access opportunities for predators. Other regular echinoid spines are long and thin, pointed, offering a more 'offensive defence' than spines such as this one.