UROCHORDATA-VERTEBRATA 



35 



Class THALIACEA 



Class LARVACEA 



Order PLEUROGONA 



Sub-order Stolidobranchiata 



Styela; Polycarpa: Botryllus; Boltenia; Pyura; 



Molgula 

 Sub-order Aspiriculata 



Hexacrobyhis 



Order PYROSOMIDA 



Pyrosoma 

 Order DOLIOLIDA 



( = Cyclomyaria) 

 Doliolum 

 Order SALPIDA 



( = Desmomyaria) 

 Salpa 



Order COPELATA 



Oikopleiira; Appendicularia: Fritillaria 



Sub-phylum CEPHALOCHORDATA ( = Acrania, Leptocardii) 



Branchiostoina { — Amphioxiis) (lancelet); 

 Asymmetron 



Sub-phylum VERTEBRATA 



Class MARSIPOBRANCHn 



( = Agnatha) 



Sub-class CYCLOSTOMATAi 



Order HYPEROARTU (lampreys) 

 ( = Petromyzones) 

 Petromyzon; Lampetra; Ichthyomyzon 

 Order HYPEROTRETI (hagfishes) 

 ( - Myxini) 

 Heptatretus ( = Bdellostoma); Myxine 



Class SELACHH 

 ( = Chondropterygii, Chondrichthyes, Elasmobranchii) 



Sub-class EUSELACHU 



Order PLEUROTREMATA (sharks, dogfishes, 

 angel-fishes) 

 ( = Selachoidei) 

 Sub-order Notidanoidea 



( - Hexanchiformes) 

 Heptranchias : Notidanus 



' See Gymnolaemata, p. 20. 



