Echinoderms
Bipinnaria larva belongs to the phylum Echinodermata. This phylum includes marine animals such as sea stars, sea urchins, and sand dollars.
Sand dolar is a simple animal. It is an invertebrate.
Sand dollars are not gastropods. Gastropods are charecterized by having a soft body with or without shell. Gastropods comes under phylum mollusca and sand dollars comes under phylum echinodermata.
Sandworms belong to the phylum Annelida, which includes segmented worms with a cylindrical body shape.
As sand dollars are animals they comes under consumer.
Phylum Echinodermata
Surprisingly, the actual name for a group of sand dollars is "a fortune." The term "sand dollar" refers to the round flat shape of the rigid endoskeleton which apparently reminded American sailors and sea-farers of a large coin when they spoted them washed up on beaches, bleached a dazzling white by the sun. This comparison to coinage and money led to the eventual use of the term "fortune" to describe a large group of these marine animals, which can congregate by the hundreds on sandbars just below the surface of the sea floor.
Salamander, Salmon, Sand Dollar, Sand Shark,
Star fishes and sea urchins are similar to sand dollars.
Sand dollars are actually an entire order of invertebrate animals. Therefor, there are many genera of sand dollars. However, the Common Sand Dollar belongs to the genus Echinarachnius.
Echinoderms are sea animals that live in salt water. There are five kind of Echinoderms, sea stars, brittle stars, sea cucumbers, sea urchins, and sand dollars. Echinoderms all are invertebrates and have internal skeletons.
The phylum Echinodermata includes animals with radial symmetry, such as sea stars, sea urchins, and sand dollars. These animals are often covered with spines and have a water vascular system that helps in movement and feeding.