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DIVISION XX. CORNIFORMES. 



GENERA. 



i. Otion. Lam. M. 



A membranous tunic 

 with an opening, at the 

 summit of which are two 

 small triangular testaceous 

 valves, separated, but ad- 

 hering to the tunic. (1) 

 Fig. 117. 



DIVISION XXI. SERIALES* 



GENERA. 



4. Chiton. Lin. M. (2) 



A series of longitudi- 

 nal, imbricated, trans- 

 verse moveable valves, 

 varying in number from 

 6 to 8, held together by 

 a coriaceous ligament, 

 sometimes shagreened, 

 hairy, and even thorny. 

 Fig. 105. 



2. Chitonellus. Lam. M. 

 (3) 



A series of longitudi- 

 nal valves, disposed like 

 a narrow ribbon on the 

 middle of the back, not 

 held together by a Hga- ? 

 ment. Fig, 106. 



(1) Northern Seas. 



(2) The valves have been found separated in a fossil state at Grignon, but the 

 ligament which held them together having been destroyed, it is difficult to 

 determine the species. Cape of Good Hope, America, European and Southern 

 Seas. 



(3) New-Holland. 



