In this article we will discuss about the structure of Heart Urchin (Echinocardium) with the help of a diagram.
2. Body heart-shaped, some-what ovoid and is having a distinct oral and aboral surfaces.
3. There is neither a central disc nor any arm present.
4. The whole body surface, oral as well as aboral, is covered over with thin, small and delicate spines.
5. The oral surface has an excentric mouth and five ambulacral areas which are naked and devoid of spines.
6. Aristotle’s lantern and madreporite are absent and anus is excentric.
7. Pedicillariae are stalked and are having three jaws.
8. The spines are borne on small tubercles and are movable.
9. Body enclosed into an exoskeleton of calcareous plates which are usually arranged into five pairs of rows and on inter-ambulacral areas.
10. Ambulacral areas are having small tube feets arranged in a row along either lateral margin.