76 CLASS VII. MOLLUSCA. 



The animals of this class reside, for the most part, in the 

 water. A few are found upon land. The former do not im- 

 mediately die on being taken out of their natural element, but 

 can live for some time in the air. They are generally carniv- 

 orous. Many of them furnish very delicious articles of food, 

 although their flesh is ordinarily heavy and difficult of di- 

 gestion. 



SECTION VIII. 

 Class VII. Mottusca. 



THIS is a large and extensive class, embracing a great va- 

 riety of animals, whose structure, residence, and habits, are 

 but obscurely and imperfectly known. Among them are the 

 cuttle-fish, squid, oyster, clam, muscle, snail, and, in short, 

 nearly all the testaceous animals, or shell-fish, as they are usu- 

 ally called, although they have no resemblance to fishes, and 

 do not all inhabit the water. As it respects their internal 

 structure and organization, they are undoubtedly superior to 

 the two classes last described ; but in regard to intelligence 

 and instinct, they are, upon the whole, inferior, and are not 

 subjects of so much interest. 



The Mollusca are destitute of bones and of articulated 

 limbs. Their bodies are generally of a soft texture, and fre- 

 quently, at first sight, appear to be little else than a simple 

 mucous mass, without parts, and almost without organization. 

 Their muscles are fixed into the skin, which is naked, very 

 sensible, and constantly moistened by a fluid furnished by its 

 pores. The contractions of these muscles produce certain 

 obscure and indistinct motions of their whole bodies, by means 

 of which they are enabled to swim and crawl, or even seize 

 those objects which are adapted to their nourishment. But 

 as no part is supported by any solid foundation, like the bones 

 of vertebral animals, their motions are generally slow, awk- 

 ward, and limited. 



Their bodies are generally covered by a fold or reflection 

 of the skin, which envelops them completely, and is called 

 their mantle. In some species, the two folds of the mantle 

 are united at their edges, so as to form a complete bag, in 

 which the body of the animal is contained, opening only at 

 one end by a sort of canal or snout : in some, it extends in 



