xiv CONTENTS 



Group III. Entomosteaca (Lower Crustacea). 



PAGE 



Order V.: Oar-Legged Crustacea ... ... ••• ••• 424 



,, VI.: Bivalved Crustacea ... ... ... ■■■ •• 424 



,, "VII.: Leaf-Legged Crustacea ... ... ■•• •■• 425 



„ VIII. : Barnacles ... ... ... ... ... ... 425 



III. Body Soft, without Jointed Limbs ; with a Ventral Organ 

 of Locomotion (Foot) ; a Fold of Skin (Mantle) above the 

 Foot, which protects the Bespiratory Organs, and usually 

 excretes a Calcareous Shell. 



III. Phylum : Mollusca 427 



(a) Asymmetrical Mollusca with Head, Flat-Soled Foot, and usually 

 Spiral Shell. 



Class I.: Gastropods ... ... ... ... ... ... ... 428 



Order I. : Air-breathing Gastropods ... ... ... ... 428 



,, II.: Gill-breathing Gastropods ... ... ... ... 434 



,, III.: Winged Gastropods ... ... ... ... ... 434 



(b) Symmetrical Molluscs without Distinct Head, with Wedge- 

 shaped Foot, and with Bivalve Shell. 



Class II.: Bivalves ... ... ... ... ... ... ... 435 



(c) Symmetrical Molluscs with Distinct Head, with Foot developed 

 into Arms surrounding the Mouth, and Posterior Funnel. 



Class III. : Cuttle-Fishes ... ... ... ... ... ... 442 



IV. Without Segmented Limbs ; Body enclosed by a Dermo- 

 muscular Tube. 



IV. Phylum : Vermes ... ... ... ... ... ... ... 446 



(a) Body consisting of Numerous Similar Segments. 



Class I.: Segmented Worms ... ... ... ... ... ... 446 



Order I. : Bristle- Worms ... ... ... ... ... 446 



,, II.. Leeches ... ... ... ... ... ... 451 



(6) Body Cylindrical, not Segmented. 

 Class II.: Thread-Worms ... ... ... ... ... 452 



(c) Body Flat. 



Class III,: Flat-Worms ... ... ... ... ... ... 454 



Order I.: Tape-Worms ... ... ... ... ... ... 454 



,, II.: Flukes ... ... ... ... ... ... 458 



