Explain the classification of phylum annelida of non chordates?

The phylum annelida is divided into polychaeta, oligochaeta and hirudinea. The polychaeta are also known as the multiple hair animals. They are marine with the fully formed parapodia and setae. They have a definite head and have separate sexes. They have eyes, tentacles etc. Their development is indirect and they do not have a clitellum. Nereis is included under it. The oligochaeta are also known as the few hair animals. They are fresh water and semi terrestrial animal. They have no head and appendages. They have few setae. They have well developed clitellum which is thick collar like swelling. They are hermaphrodite and copulate by cross fertilization and results in the ootheca formation. No metamorphosis occurs. Indian earthworm is included in this class. The hirudinea are also known as leech. They are parasites and have couple of suckers like anterior and posterior. No tentacle or parapodia are present. They are hermaphrodite and copulate by cross fertilization. They have the internal method of fertilization. They have haemocoelomic system. Their development is direct and they occur in fresh water mainly. They have clitellum and below the layer of muscle they have botryoidal tissue. This is a unique connective tissue.