42 THE ELEMENTS 



The next tbinor to be taken into 

 consideration, is the genera compos- 

 ing the three orders of shells. 



OF GEJVER^. 



ORDER FIRST. 



MULTIVALTE SHELLS. 



Animals soft, of a simple structure, 

 and covered with a calcareous habita- 

 tion or shell. 



Genus 1st. — CHITON. Animal In- 

 habitino' the shell a Doris; shell con- 

 sisting of several segments or valves, 

 placed transversely on the back of the 

 animal, and Ijing upon each other at 

 their anterior edge. Linncean Syst. 

 No, 800. 



