CONTENTS 



SECTION XIII 



PAGE 



PHYLUM CHORDATA . 



Sub-phylum and Class I. Adelochorda . 1 



Sub-phylum and Class II. TTrochorda . H 



1. Example of the Class Ascidia . 12 



2. Distinctive Characters and Classification . 18 

 Systematic Position of the Example . . 20 



3. General Organisation . 20 



Sub-phylum III. Vertebrata 37 



Division A. ACRANIA 38 



,, B. CRANIATA 58 



Class I. Cyclostomata . 115 



1. Example of the Class Petromyzon . . 116 



2. Distinctive Characters and Classification . .128 



3. Comparison of the Myxinoids with the Lamprey . . 129 



4. General Remarks ... . . 132 



Class II. Pisces . 134 



Sub-class I. Elasmobranchii . . . 134 



1. Example of the Class Scyllium canicula or Chiloscyllhnn 



fuscum 135 



2. Distinctive Characters and Classification . 154 



3. General Organisation .... .157 



Sub-class II. Holocephali . 173 



