Razor shells or something else?

Spotted these on a dive in the Maldive last week.  At first I thought they were some kind of razor shell but also wondered if it was just spines of a lion fish hiding in a hole although they seemed a bit thick for that.

My guess would be slate pencil urchin (https://en.wikipedia.org/wiki/Heterocentrotus_mamillatus)

I hadn't thought urchin, again because of the width of the spines, but that's very likely what it was.

Thank you.