CONTENTS. XI 



Page 



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



Sub-Sect I. The Order of Gasteropoda proper . l . /*. 477 



II. The Order of Heteropoda .... 488 



IIL The Order of Pteropoda -' .v ; ' V" ! . 489 



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



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



IL 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 Discophorae, or Medusas proper 509 



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



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



Sub-Sect I. The Order of Alcyonaria . !: ~V - . . 519 



IL 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 



