This is a bargain, 2.4" long specimen of the super spiny trilobite Comura bultyncki from the Tazoulait Formation of Morocco. There are nearly 40 free-standing spines. You can even see the tiny eye facets in it's eyes. There preparation is a big rough in a few areas leaving a few scratches on the shell and a small number of the spines are composites (the vast majority are original), hence the bargain price.
Trilobites were a very diverse group of extinct marine arthropods. They first appeared in the fossil record in the Early Cambrian (521 million years ago) and went extinct during the Permian mass extinction (250 million years ago). They were one of the most successful of the early animals on our planet with over 25k described species, filling nearly every evolutionary niche. Due in large part to a hard exoskeleton (shell), they left a excellent fossil record.