The structural deference between them is that Sea urchins are more globular whereas sand dollars are flattened.
Unlike sea urchins, the sand dollars burrow themselves when threatened.
Sand dollars have anus opening at their back side whereas the sea urchins have it at the top.
they both have spines but the sea urchin is round while the sand dollar is flat
Star fishes and sea urchins are similar to sand dollars.
No. They are invertebrates related to starfish and sea urchins.
Sea urchins and sand dollars.
They both or found in the ocean
Sand Dollars are the carcasses of dead sea urchins, and when alive, they eat though a mouth.
Yes they are. They are flattened burrowing sea urchins.
You are misidentifying the animals as sand dollars (Mellita), when in fact they are 6-holed sea urchins.
sea stars, sea urchins, sand dollars, and sea cucumbers.
Starfish, sea urchins, sea cucumbers, and sand dollars.
Echinoderma are a phylum of "spiky skin" sea life, such as starfish, sea urchins, and sand dollars.
No - sea urchins are part of the echinoderm phylum, with sand dollars, starfish and sea cucumbers.
Sand dolar is a simple animal. It is an invertebrate.