CONTENTS xvii 



PAOK 



Piivii m A i; i iikopoda — continued. 



Class IV. Insecta 619 



1. Example of the Class — Periplaneta oriental™ 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 — Euscorpio or Buthus 653 



2. Distinctive Characters and Classification 660 



3. General Organisation 662 



Appendix to the Arachnida — the Pycnogonida, LinguatulicUi, 



and Tardigrada 673 



Relations of the Air-breathing Arthropoda 676 



SECTION XII 



Phylum Molixsca 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 



