what kinda urchin is this (pic)?
http://img146.imageshack.us/img146/5515/cimg1462.jpg
About 3/4 inch wide now. came with a rock. The lower spines are kind long and blunt and get shorter to the top.
Got a slightly better pic. kinda tough since the urchin is solid black and rather small. http://img132.imageshack.us/img132/7311/cimg1497h.jpg
No idea where the rock came from aside from out of the LFS, uncured. The urchin hides somewhere in the rock at night and moves all over it's rock during the day. Very territorial as it don't normally leave rock or a 5"x5" square area.
As it's been growing, It starts to appear that it's spikes go in rows vertically like a tuxedo's. A lot of times when it is out grazing on the rock during the day, it will excrete white stuff that looks like large grains of crushed coral sand from the center top. Only other thing I can describe on it is that the spines are not point nor flat but strait with smooth rounded ends.