GENUS I. CHITON. 43 



partmcnts : one, wliicli may be called Ihe middle division^ 

 stretches across the shell, or lengthways of the valves (^pl. 1. 

 /. I. a); the others may be called the side divisions Q)l. 1. 

 /. 1. b b~). When these divisions are marked with lines across 

 the Aalves (^pl. 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 Q)L 1, /. 1. b^, they are said 

 to be longitudinally striated. 



Linneeus has described, in his twelfth edition of Systenui 

 Naturce, 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- 

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

 iiis MoUusca 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 (^pl. 1. /. 1. 

 CJiiton squamoms). 



g2 



