Here is a classic rhynchonellid brachiopod with a strongly ridged shell. The example top left shows the pedical opening very clearly. A fleshy stalk, the pedicle, extended from this hole and anchored the shell to the sea floor. This is one of the fundamental differences between these ancient sea shells and nearly all of the modern sea shells we find on the sea shore today.
Find out more on the brachiopods page.