CHAPTER X 

 PHYLUM MOLLUSCOIDEA 



The phylum Molluscoidea contains three classes which agree 

 in the possession of a ridge called the lophophore at the anterior 

 extremity of the body bearing a crown of ciliated tentacles. The 

 three classes: Polyzoa, Brachiopoda, and Phoronida, present so 

 many individual peculiarities that few statements may be made 

 that would apply equally to the organization of the members of 

 all three. Consequently, the structure and characteristics of 

 the individual classes will be discussed separately. 



Fig. 80. — Diagrams to show contrast in general organization in; A, an endo- 

 proct bryozoan; B, an ectoproct bryozoan. The digestive system is shown in 

 solid black. Compare the position of the anal opening in the two figures. 

 iOrig.). 



Class Polyzoa 



Individuals of the class Polyzoa (or Bryozoa) bear very close 

 superficial resemblance to hydroid polyps from which they are 

 readily distinguishable because the polyzoan zooids possess a 



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