1) Animal order 2) Heart-shaped sea urchins 3) Order spatangoida 
The heart urchins or Spatangoida are an order of sea urchins. Their body is a somewhat elongated oval in form, and is distinguished by the mouth being placed towards one end of the animal, and the anus towards the other. As a result, heart urchins, unlike most other sea urchins, are bilaterally symmetrical, and have a distinct anterior surface. Th...
[n] - heart-shaped sea urchins
order Spatangoida noun heart-shaped sea urchins