CLASSIFICATION AND DISTRIBUTION 377 



Division II. METAZOA: many-celled animals with a differ- 

 entiation of cells. 



Phylum I. PORIFERA: animals with no distinct mouth, but 

 many incurrent openings : the sponges. 



Class I. Calcarea: with a skeleton of calcareous spicules. 

 Class II. Non-calcarea: with a skeleton of silicious or 

 horny spicules, or none. 



Phylum II. CCELENTERATA: animals with a mouth, but 

 without an anus and with no body cavity. 



Class I. Hydrozoa (Fig. 69). 



Class II. Syphozoa: sea-nettles. 



Class III. Actinozoa: corals, anemones. 



Class IV. Ctenophora. 



Phylum III. ECHINODERMATA: radiate animals, with com- 

 plete alimentary canal and a body cavity. 



Class I. Asterioidea: starfishes. 



Class II. Ophiuroidea: brittle stars. 



Class III. Echinoidea: sea-urchins. 



Class IV. Crinoidea: sea-lilies. 



Class V. Holothuroidea: sea-cucumbers. 



Phylum IV. PLATYHELMINTHES : flat, unsegmented 



worms. 



Class I. Cestoda: the tapeworms. 



Class II. Trematoda: the flukes. 



Class III. Turbellaria: the planarians. 



Phylum V. NEMATHELMINTHES : round, unsegmented 

 worms: round worms, threadworms. 



Phylum VI. MOLLUSCOIDEA. 



Class I. Polyzoa: sea-mats, corallines. 

 Class II. Brachiopoda: lamp-shells. 



