LECTURE XL 



JL HE Linnaean Mollusca Testacea, or Soft-bo- 

 died Animals furnished with Shells, are divided into 

 three assortments, called Univalves, Bivalves, and 

 Multivalves ; meaning, that the shelly cover con- 

 sists either of one, two, or several parts or valves. 



A Univalve Shell may be exemplified by that 

 of the common snail ; for the shell is simple or un- 

 divided. A Bivalve Shell may be exemplified by a 

 Muscle, in which, as every one knows, the shell is 

 composed of two pieces or valves ; and lastly a 

 Multivalve Shell may be exemplified by any spe- 

 cies of Lepas or Bernacle, in which the shelly co- 

 vering of the animal is formed of several pieces or 

 divisions. 



The animals inhabiting by far the greater part 

 of the Univalve shells are formed on the plan of 

 the common Garden Snail, to which they bear a 

 great general resemblance, though furnished, in 



