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vexity towards the margins. They are variously stri- 

 ated, or minutely granulated; and one extremely rare 

 species has callous adhesions longitudinally placed 

 along the back of the valves. Many species of Chiton 

 are elegantly marked; the interior is generally of a 

 green or white color ; one species is, however, of a beau- 

 tiful pink. They adhere to rocks covered by the sea, 

 to tortoises, and to the backs of fishes, &c. 



The writer has carefully examined many hundred 

 examples of this genus, each possessing eight valves, 

 but has never seen one with a less number. Whenever 

 such an occurrence has taken place, it should probably 

 be considered a lusus, and not characteristic of a dis- 

 tinct species. 



Sowerby mentions that the fossil species are rare, 

 but that detached valves are sometimes found in the 

 calcareous sand in the neighbourhood of Paris. The 

 C. gigas sometimes attains four inches in length. 

 Chiton gigas Chiton spinosus 



squamosus fascicularis 



Peruvianus marginatum 



