sentences:  The coast of Southern California is known as a source of high quality uni, with divers picking sea urchin from kelp beds in depths as deep as 24 m/80 ft. As of 2013, the state was limiting the practice to 300 sea urchin diver licenses.In the Pacific, bunches of heavy spines from slate-pencil urchins ("Heterocentrotus" species) were used as abrasion tools for shipbuilding.Some species of sea urchins, such as the slate pencil urchin ("Eucidaris tribuloides"), are commonly sold in aquarium stores.