Hi, several months ago i found a very tiny and rather flat urchin in a block which had two spines. I managed to disengage the urchin, but it is really too tiny for my camera. The spines are bigger and i wondered to what family of urchin they belong (maybe a cidarid ?)
I also join the photos of the urchin that was with them (although i don't know if that would help).
@Coco @caterpillar ?
The smallest spine :
The bigger :