94 



CLASS VI. CRUSTACEA. 



Remarks. These animals were placed in the 

 class Insecta by Lineas. There was no difficul- 

 ty in this arrangement, as the characters are defi- 

 nite and constant. The separation is generally 

 approbated. In truth there seems to be a wide 

 difference between a lobster and a butterfly. But 

 some species of the class Insecta have something 

 of a crust, which causes many naturalists to ques* 

 tion the beneficial uses of this subdivision. 



They respire by a kind of gills or lamellar py- 

 ramids, sometimes furnished with threads. These 

 are placed at the articulations of the body. They 

 generally have four antennse. Their crustaceous 

 covering is very strong in some species, as the lob- 

 ster ; in others it is thin and tender. 



The crusts of some species have been found iu 

 the state of petrifactions or relique. But I do not 

 think Brongniard has demonstrated the trilobite 

 to have been of this class. I have recently found 

 trilobites in a calciferous slate, with their carbo- 

 nate of lime shells still remaining. I believe M, 

 Brongniard will hereafter convince himself that 

 the trilobite was a rnultivalve molluscous animal, 



ORDER l. DECAPODIA. 



Head confounded with the trunk* 



CANCER, (crab, lobster,) having ten feet ; head 

 united to the corslet, forming a shield, covering 

 the whole anterior part of the body. 



