Phylum - Echinodermata

Discuss the characters of the phylum Mollusca or Echinodermata.

Mention the classes of the phylum Mollusca or Echinodermata. Give their distinguishing features and examples.

Discussion Class-3 Phylum Mollusca || Echinodermata || Hemichordata || Chordata || Cephalochordata || Pisces || Superclass

Nematoda || Arthropoda || Annelida || Mollusca || Echinodermata || Chordata

Member of Echinodermata has a specific system, which is not found in other phylum, it is :-

How many from the following phylum has external fertilisation with indirect development ? {Porifera, Ctenophora , Echinodermata, Hemichordata }