GENUS I. CHITON. 43 



partnients : one, which may be called the middle division, 

 stretches across the shell, or lengthways of the valves (p/. 1. 

 /. 1. a); the others may be called the side divisions (^j)l. 1. 

 f. I. b Z>). When these divisions are marked with lines across 

 the valves QiL 1. /, 1. a), they are said to be transversely 

 striated ; but when they are marked with lines lengthways of 

 the valves, that is, across the shell Qj/. 1. /. 1. b}, they are said 

 to be long'itudinally striated. 



Linnaeus has described, in his twelfth edition of Systema 

 Natiii'ce, only 9 species ; Gmelin has added 19^ and Dr. Turton 

 none : making in all 28. Adanson considers the Chiton as a 

 sort of Patella. 



Lamarck has placed the Chiton, under the name of Osca- 

 brion, as well as Bulla aperta and Helix Haliotoidea, among 

 his Mollusca with Heads, Naked, and which creep on the 

 Belly; he says it is covered with a skin furnished in the 

 middle with a row of testaceous pieces transversely set in the 

 thickness, and more or less appearing outwardly Qpl, 1. /. 1. 

 Chiton squamosus). 



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