41 



DEFINITIONS and DESCRIPTIONS 



OF 



THE GENERA. 



MVLTIFALVES. 



CHITON. 

 (See Plate III. fig. 1.) 



V ALVES many; disposed in an imbricated manner, 

 or with the edges one over another, along the back. 



The general form of the shell is convex-oval, 

 and the maigins of the valves are connected by an 

 elastic, coriaceous cartilage, often scaly, hairy or 

 spinous, which permits the free motion of the 

 valves, or segments, in a longitudinal direction. 



The Chiton much resembles the Oniscus ento- 

 mon, or marine woodlouse, and has often been mis- 

 taken for it. It is capable, in the same manner, of 

 rolling itself into a perfect ball. 



