GENERAL CLASSIFICATION. 475 



General Classification of Phylum Chordata 



Class HYPOSTOMATA (extinct). 



Class CYCLOSTOMATA (Round Mouths), without true jaws. 

 Myxine, hag-fish. Petrotnyzon, lamprey. 



SUB-PHYLUM CEPHALOCHORDA. Amphi- 

 oxus or Lancelet. 



{Salpa type. 

 Ascidian type (sea- 

 squirts). 

 Appemiicularia (lar- 

 val type persistent). 



Surviving offshoots of ancestral Vertebrates. 



PHYLUM HEMICHORDA or ENTEROPNEUSTA (offshoots of incipient Vertebrates?). 

 BalanoglossuS) etc. ; probably Cephalodiscus \ possibly Rhabdopleura. 



Ancestry of Vertebrates 



It is not at present possible to trace the path along which Vertebrates 

 have evolved, though our faith in the doctrine of evolution as a moda. 



