42 

 CHAPTER IV. 



OF THE CHITON. GENUS I. 



CHITON. 



"Animal a Doris. Shells many, longitudinally disposed, covering the 

 back." — Linn. 



The shells composing this genus are easily distingvtished from 

 all others. They are of an oval form (/. 1. pi. 1), somewhat 

 resembling the Oniscus or common Wood Louse : the shell 

 does not inclose the animal, but only covers the back of it : 

 it is composed generally of eight pieces called valves, sur- 

 rounded by a narrow belt or margin, which is sometimes 

 covered with scales (p/. 1. /. 1. c c). Some few shells have 

 been found with only six or with seven valves, but they are 

 probably accidental varieties. The animal is somewhat similar 

 to that inhabiting the Patella, but is not capable like that of 

 protruding the head beyond the margin of the shell ; the head 

 is nearly crescent-shaped, without any appearance of either 

 eyes or horns : it appears to belong to the family of Slugs, or 

 the Limax of Linnaeus. They are all inhabitants of the sea, 

 and are generally found creeping on the rocks, or attached to 

 stones, to other shells, or to sea- weeds, and not unfrequently on 

 Oysters on the coast of South Devon. 



The valves, excepting the first and last, are often striated in 

 two different directions that divide each valve into three com- 



