162 CLASS-BOOK OF ZOOLOGY. 



QUESTIONS ON SECT. XLII. 



684. What are Corals? 



685. How are islands formed by stony Corals ? 



686. In what consists the injury done by Corals? 



687. What do you know of the body of Sea-polypes ? 



688. Describe the Red Coral. How is it obtained ? 



689. Where is it collected, and where manufactured into several arti- 

 cles of art? 



690. Describe the Horn-coral. 



691. What are Sea-brooms and Sea-fans ? 



692. Where are they found, and what is then* size and singularity ? 



SECTION XLIII. 



3c? Order — Shellfish : ( Testacea, Lin.) 



\ 693. Shellfish are those worms which are enclosed 

 in a calcareous shell ; as Clams, Snails, etc. 



§ 694. The calcareous substance of Shell-fish is grad- 

 ually formed, as the creature grows, from the slimy fluid 

 of its body, which attaches itself to the edge of its opening, 

 becomes solid, and increases the size of the shell. 



§ 695. Many of the shells are deserving of notice for 

 their wonderful structure ; others for their glittering por- 

 celain-like glazing, their splendid colors, or their regular 

 and delicate marks ; while many of them are interesting 

 from their importance as articles of food for man. 



§ 696. Shellfish are more perfect than the preceding 

 Orders, as they are provided with arteries and veins, with 

 a heart and liver, and some of them with a head and eyes. 



§ 697. The lower extremity of their body, which is 

 musculous, is in many species prolonged to enable the 

 animal to move its body ; which prolongation, for that 

 reason, is called a foot, as in snails. 



5 698. The wisdom of the Creator has covered these 

 delicate animals with hard shells, to preserve their soft 

 bodies from injury, embellishing them, at the same time, 

 with elegant forms and the most splendid colors. 



