ClipArt ETC
<i>Amphidotus cordatus</i> or <i>Echinocardium cordatum</i>, commonly called a sea urchin, viewed from above. a, anterior ambulacrum, forming with b, b, anterolateral ambulacra, the trivium; c, c, two posterolateral ambulacra, forming the bivium; d, madreporic tubercle surrounded by genital pores; e, intrapetalous semita or fasciole; f, circumanal semita." &mdash;Whitney, 1889

Sea Urchin - View from Above

Amphidotus cordatus or Echinocardium cordatum, commonly called a sea urchin, viewed from above. a, anterior…