Some Pencil species, such as the Caribbean species Eucidaris tribuloides, are meat-eating animals, says Ronald Shimek in his There's No Reason To Be Spineless article. He states that, "Before I found this out in my own system, I watched a Pencil Urchin (Eucidaris tribuloides) catch and eat a scarlet cleaner shrimp".
This is from one of several sites, along with my LFS, that say that pencil urchins will catch shrimp and small fish while they are sleeping and eat them.