HRS 804 Carboniferous, Polished section through Crinoidal limestone
Crinoids also known as 'sealilies' were once present in vast numbers in the warm tropical seas of the Carboniferous era. They had a calcareous stem attached to the seafloor or a rock, a stem often several feet in length made up of ossicles or small circular or elliptical plates. At the top of this spine or stem was a cup and from there arms radiated outward. The central part had both mouth and anus. Usually the commonest fossil remains are of the stem ossicles or plates which look like little Polo mints joined together. The photo shows a polished piece of limestone with sections through the crinoid stems.