CONTENTS. XI 



Page 



SECT. II. THE CLASS OF GASTEROPODA, OR GASTEROPODS 476 



Sub-Sect. I. The Order of Gasteropoda proper . . . 477 



II. The Order of Heteropoda . . . . 488 



III. The Order of Pteropoda . . . .489 



SECT. III. THE CLASS OF ACEPHALA, OR ACEPHALS . 489 



Sub-Sect. I. The Order of Lamellibranchiata . . . 489 



II. The Order of Tunicata, or Ascidians . . 495 



III. The Order of Brachiopoda, or Brachiopods . 496 



IV. The Order of Bryozoa, or Bryozoans . . 497 



CHAPTER V. 



THE BRANCH OF RADIATA, OR RADIATES .... 498 



SECT. I. THE CLASS OF ECHINODERMATA . . . 498 



Sub-Sect I. The Order of Holothurioids, or Holothurians 499 



II. The Order of Echinoids, or Sea-Urchins . 500 



III. The Order of Asterioids, or Star-Fishes . 503 



IV. The Order of Ophiurioids, or Ophiurans . 504 

 V. The Order of Crinoids .... 505 



SECT. II. THE CLASS OF ACALEPHS, OR JELLY-FISHES . 506 



Sub-Sect I. The Order of Ctenophorae, or Beroid Medusae 508 



II. The Order of Discophorse, or Medusae proper 509 



III. The Order of Hydroidre, or Hydroids . . 512 



SECT. III. THE CLASS OF POLYPI, OR POLYPS . . . 517 



Sub-Sect. I. The Order of Alcyonaria . . . .519 



II. The Order of Actinaria .... 522 



III. The Order of Madreporaria .... 524 



CHAPTER VI. 



THE GEOGRAPHICAL DISTRIBUTION OF ANIMALS . . 529 



CHAPTER VII. 



CONCLUDING REMARKS 533 



INDEX 536 



