266 ARTICULATA. 



CLASS I. CRUSTACEA.* 



THE first three Classes of Articulated animals 

 are sometimes called Condylopes,^ from their being 

 furnished with jointed feet, of which the fourth is 

 destitute. They were included by Linnaeus in his 

 Class Insecta ; but, though they possess many cha- 

 racters in common, there are essential differences 

 between them. They have often more, never less, 

 than six feet; their crust is generally horny in 

 texture, more especially on the limbs; each joint 

 is hollow, and contains the muscles of the succeed- 

 ing one. The mouth is furnished with two pairs 

 of jaws, which move transversely, and with certain 

 jointed organs called palpi, whose office is not fully 

 known ; the head has, in general, one or more pairs 

 of jointed filaments, resembling the palpi, but usu- 

 ally more developed and more diversified in form, 

 termed antenna. These projections have been, by 

 various naturalists, supposed to be the organs of 

 touch, of smell, of hearing, or of a sense not con- 

 ferred upon us, and therefore of which we can have 

 no idea. They are always furnished with eyes, 

 which are hard, horny, and projecting : these are 

 of two distinct kinds, one consisting of a simple 



* Crusta, the shell of a lobster, &c. 



s, kondyhs, a joint, and vrov$,pous f a foot. 



