CONTENTS xvii 



PAGE 



PHYLUM ARTHROPODA continued. 



Class IV. Insecta . 619 



1. Example of the Class Periplaneta orientalis or P. americana . 619 



2. Distinctive Characters and Classification 631 



Systematic Position of the Example . . 636 



3. General Organisation . . ... . 636 



Class V. Arachnida . . . 653 



1. Example of the Class Enscorpio or Bit thus 653 



2. Distinctive Characters and Classification . ... 660 



3. General Organisation 662 



Appendix to the Arachnida the Pijcnoyonida, Linguatulida, 



and Tardigrade 673 



Relations of the Air-breathing Arthropoda 676 



SECTION XII 



PHYLUM MOLLUSCA . 680 



Class I. Pelecypoda . 680 



1. Example of the Class Anodonta and Unio 680 



2. Distinctive Characters and Classification 694 



Systematic Position of the Examples 696 



3. General Organisation . . . ... 696 



Class II. Amphineura . 712 



1. Distinctive Characters and Classification 712 



2. General Organisation . .... 713 

 Class III. Gastropoda ... . 721 



1. Example of the Class Triton nodiferus .... . 721 



2. Distinctive Characters and Classification . ... 732 

 Systematic Position of the Example .... . 734 



3. General Organisation . . . 735 

 Appendix to the Gastropoda . .... 756 



A. Class IV. Scaphoda . 756 



B. Rhodope . . 758 

 Class V. Cephalopoda . . . 759 



1. Examples of the Class 759 



i. Sepia, .... 759 



ii. Nautilus pompilius . 776 



2. Distinctive Characters and Classification 789 



Systematic Position of the Examples .... . 790 



3. General Organisation . 790 



General Remarks on the Mollusca 804 



VOL. I 



