Fossil of hard shell sea urchin
The hard shelled sea urchin, when viewed from the side, has a huge conical shell with a flat base. The petals are short and wide, very conspicuous, and are specifically used for respiration. When alive, the petals also have tubular feet, and the bony plates in the step zone are short and wide. The mouth is located at the center of the lower surface and has 5 distinct protrusions, hence it is star shaped. The anus is located behind the upper surface and originally had many short, slender shell needles on the surface. The cone shape of juvenile specimens is not obvious. It is common on the surface of sandy limestone in the eastern United States.
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