CONTENTS 



SECTION XIII 



PAGE 



PHYLUM CHORDATA 1 



Sub-phylum and Class I. Hemichorda (Adelochorda) .... 2 



Sub-phylum and Class II. Urochorda 13 



1. Example of the Class Ascidia 14 



2. Distinctive Characters and Classification 20 



Systematic Position of the Example 23 



3. General Organisation 23 



Sub-phylum III. Euchorda 42 



Section I. ACRANIA 43 



Section II. CRANIATA 63 



Class I. Cyclostomata 119 



1. Example of the Class Petromyzon 119 



2. Distinctive Characters and Classification 133 



3. Comparison of the Myxinoids with the Lamprey . . . .134 



4. General Remarks 138 



Class II. Pisces 139 



Sub-class I. Elasmobranchii 140 



1. Example of the Sub-class Scyllium canicula or Hemiscyllium 



modestum 140 



2. Distinctive Characters and Classification 161 



3. General Organisation 165 



53 4 S 



