INTRODUCTORY CHAPTER. 11 



2. CoNCHiFERA, (_shell-bea)-i>ig animals,) with a shell, consisting 



of two valves, as an oyster or mussel. 



3. CmnuiFhDA, (uith feet like cirri, or hairs.) The inhabitant 



of the acorn-shell, found on the back of the larger kind of 

 shell-fish, &c., is an instance of this class. 



4. Annelida, (with body formed of rings ;) of this class the 



leech and the earth-worm are instances. 



5. Crustacea, (covered ivith a liard case,) crabs, lobsters, &c. 



6. Arachnid.-e, Spiders. 



7. IssECTA, Insects. A perfect insect has always six legs. 



8. TuNiCATA, (enclosed in a case of a leathery consistence.) 



9. Vermes, ]Vorms. With lengthened body without divisions ; 



for instance, worms found in the intestines. 



10. Radiaki/e, (radiated animals,) with the different parts of 



which they are formed arranged like rays round one com- 

 mon centre ; as, for instance, the Star-fish. 



11. Fo-L\Fi, (many feet.) The animal that forms tlie Coral is a 



Polypus. 

 r2. Infl'soria, (Infnsory animals.) These are found in infu- 

 sions of vegetable substances in water, and are, in general, 

 too small to be visible to the naked eye. 



In the present little book we shall treat of th^ first 

 five of these Classes. 



The Molluscous animals are, on account of their orga- 

 nization, placed first among the invertebial animals, a 

 few of the species resembling, in some respects, the 

 more simply-formed fishes. 



The systematic arrangement of the Molluscous ani- 

 mals, considered not only as regards their shells, but 

 having reference also to the anatomical distinctions of 

 the creatures themselves, is a modern study. In ancient 

 authors we merely find a few scattered facts, the beauty 

 of the shells attracting their notice more than the value 

 or nature of the animals. 



B 2 



