Notochord is confined only to larval tail in
Notochord is confined to larval tail in Doliolum, which is an urochordate.
Amphioxus is a cephalochordate in which notochord is persistent throughout the life.
Dentalium (Mollusca) is without a notochord.
Myxine (Cyclostome) has cartilaginous endoskeleton with a persistent notochord.