CONTENTS 



SECTION XIII 



PAGE 



PHYLUM CHORD ATA . 1 



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



Sub-phylum and Class II. TJrochorda ....... 14 



1. Example of the Class Ascidia ........ 14 



2. Distinctive Characters and Classification . -, . . . .21 

 Systematic position of the Example ....... 24 



3. General Organisation ......... .24 



Sub-phylum III. Euchorda ......... 43 



Section I. ACUANIA ........... 44 



Section II. CKANIATA . ........ 65 



Class I. Cyclostomata .......... 123 



1. Example of the Class Petromywn ....... 124 



2. Distinctive Characters and Classification ..... 137 



3. Comparison of the Myxinoids with the Lamprey .... 138 



4. General Remarks ......... . 142 



Class II. Pisces ............ 144 



Sub-class I. Elasmobranchii ' ........ 144 



1. Example of the Sub-class -Scylliurii cnmc-ula or Ifemiacylliitm 



. ......... . 144 



2. Distinctive Characters and Classification ..... 166 



3. General Organisation ......... 170 



