SIMPLIFIED LIST OF RECENT CLASSES AND ORDERS 22 



Class Subcl Order 

 Irregularia 



Holectypoida 



Cassiduloida 



Clypeastroida cake-urchins, sand-dollars 



Spantangoida heart-urchins 

 HOLOTHURIOIDEA sea-cucumbers 



Aspidochirota 



Elasipoda 



Dendrochirota 



Molpadonia 



Apoda 



PTEROBRANCHIA 



PTEROBRANCHIA 



Rhabdopleurida 

 Cephalodiscidea 



ENTEROPNEU STA 



acom-worms, tongue-worms 



ENTEROPNEUSTA 



Balanoglossida 



PLANCTOSPH AEROI DEA 

 PLANCTOSPHAEROIDEA 



Planctosphaeroidea 



TUN ICATA 



tunicates 



LARVACEA 



Larvacea 

 ASCIDIACEA sea-squirts, ascidians 



Stolidobranchiata 



Aspiraculata 



Phlebobranchiata 



Aplousobranchiata 



Octacnemida 

 THALIACEA 



Pyrosomata 



Pyrosomatida 

 Myosomata 



Cyclomyaria 



Hemimyaria 



Desmomyaria 



