A molluscan with calcareous spicules is

What are spicules ?

The molluscan with out a shell is

Characters of a phylum are given below. Read them carefully and answer the questions : : (a) Spines of calcium carbonate are present on the body. (b) These animals are exclusively marine. (c) They perform the locomotion with the help of tube feet. (d) Their skeleton is made up of calcareous plates or spicules. Give an example from that phylum.

Molluscan heart is

Molluscan heart is

Box like calcareous test occurs in