216 



MOLLUSKS: ACEPHALS. 



worms. The common kinds are about a foot long, but 

 one kind is three feet in length. They bore into the 

 timber of ships and wharves. 



Fig. 452. — Common Clam. Re- 

 duced. Coast of New England. 



Fig. 453. — Pandora. 



Fig. 454. — Gnstrochsena. Fig. 455. - 

 Galway. 



- Watering-pot Shell. Much 

 reduced. 



Fig. 456. — Pholas. 

 India. 



Reduced. 



Fig. 457. — Pholas. New 

 England and eastward. 



Fig. 458. — Tunicate. 



TUNICATES. 



These are mollusks which have no 

 shell, but are covered with a tough 

 tunic, or skin. Sometimes they grow 

 in clusters, attached by a stem to sea- 

 weed, rocks, or floating timber. They 

 vary from the size of a pea to an 

 inch or more in diameter. They 

 are sometimes called Ascidians, from 

 a word which means a leather lag. 



