Sand Dollar or Sea Biscuit

I'm not quite sure if this is considered a sand dollar or a sea biscuit. I'm from NJ and the sand dollars on the East Coast have holes on the edges and top. This one is from the Washington coast and I left it in it's natural state to make this ornament. The next one will be bleached and cleaned to see if I can make it a brighter white.
 I used the photopolymer stamp from Flourishes "Coastal Christmas" set and it was not too difficult to stamp it carefully onto the slightly rounded shell. Colored with Copic markers. You have to sort of dab the color on since the shell is rough and will tear up your nib if you try to color back and forth. I braided some bakery twine for the hanger. Can't wait to add this to my beach tree next season. I had the most difficult time finding beach/shell themed ornaments out here in the Pacific Northwest. They were a lot easier to come by at my previous home on the Jersey Shore :)