PART III 



COMPARATIVE ZOOLOGY OF 

 CHORDATES 



Outline Classification of the main groups of Chordate animals, 

 showing the meaning and value of the comprehensive terms 

 employed. For complete classification, see p. 487. 



(Most of the extinct groups have been omitted.) 



Phylum. 

 Subphylum. 



Subphylum. 

 Class. 



Class. 



Subphylum. 



Grade. 



Branch and Class. 



Branch. 



Chordata. Animals with gill-slits, notochord, 

 dorsal tubular nerve-cord, and 

 post-anal tail. 

 Hemichordata. Very lowly forms with a 

 small notochord only in the 

 anterior region of the body, 

 e.g. Balanoglossus. 

 Protochordata. Without a specialised head 

 or skull. . 



Urochordata. Degenerate forms with a 

 notochord only in the tail of 

 the larva, e.g. Ascidia. 



Cephalochordata. Primitive forms with 

 the notochord extending the 

 whole length of the body, e.g. 

 Amphioxus. 

 Craniata. With a specialised head and skull, 

 paired eyes, ears, and noses, 

 heart and coelomostomic 

 kidneys. 

 Anamnia. Without an amnion. Breath- 

 ing by gills at some stage of 

 life if not altogether. 



Cyclostomata. With a round sucking 

 mouth, no jaws or paired fins, 

 e.g. Petromyzon (lamprey) 

 Myxine (hag). 



Gnathostomata. With biting jaws, 

 stomach, paired fins or limbs, 

 Wolffian and Miillerian ducts. 

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