PHYLUM IX, MOLLUSCOIDEA 



The Molluscoidea are aquatic, usually marine animals with 

 a well-developed digestive canal. There is a tentacle-bearing 

 ridge (lophophore) surrounding the mouth. This ridge is 

 partly respiratory in function. A nerve ganglion is present 

 dorsal to the oesophagus. The soft parts of the body are sup- 

 ported and protected by a calcareous, corneous or membra- 

 nous covering. 



Derivation of name. — Molluscoidea > English Mollusca -\- 

 Greek eidos (old), form. The external, bivalve shell of the class 

 Brachiopoda bears some resemblance to the molluscan shell 

 of the class Pelecypoda. 



The Molluscoidea are divided into the following classes : 



Page 



A. Bryozoa 173 



B. Phoronida 181 



C. Brachiopoda 181 



CLASS A, BRYOZOA 



Type of class, — Bugula avicularia (Hving) (Fig. 69). 



The most common species on the Atlantic coast, from North 

 Carolina to Maine is Bugula turriia. This may be used in the 

 laboratory in place of B. avicularia. 



This is a colonial form, growing in tufts two or three inches 

 long on piles or rocks on the seashore in all parts of the world. 

 The colony (zoarium) is made up of erect stems, attached by 

 root-like fibers to the rock or other support. Each stem con- 

 sists of four parallel rows of closely arranged zoKcia, — the 

 individual cups. On nearly all zooecia is an appendage, the 

 avicularium, with very much the appearance of a bird's head, 



173 



