How are trilobites and horseshoe crabs similar? how they are dissimilar?

Question

How are trilobites and horseshoe crabs similar? how they are dissimilar?

Answer 1

Both are arthropods

'The closest extant relatives of trilobites may be the horseshoe crabs, according to (Fortey 2000), or the cephalocarids, according to (Lambert 1985).'

so they are related, but trilobites are extinct whilst horseshoe crabs are still alive today.

Wiki links down the bottom, with plenty of info.