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CHAPTEK XVI. 



CEPHALOPODOUS MOLLTJSCA. 

 " Monstrum horrendum, informe, ingens." VIKGIL. 



THE highest class of Molluscs is the Cephalopoda, which has been 

 divided by Professor Owen into two Orders, Tetrabranchiata, or 

 animals having four branchiae, and the Dibranehiata, having two 

 branchiae. The first Family of the Tetrabranchiata, having the 

 Ammonitidae, contains the fossil Turrilites and Ammonites. The 

 second Family, Orthoceratidte, contains the fossil Gomphoceras and 

 Orthoceras. The third Family, Nautilidte, contains Nautilus. 



The name Cephalopoda, as already stated, is taken from the posi- 

 tion of the feet, which are inserted in the anterior part of the head : 

 in Greek /ce<j>a\}], head, and Tiovs-TroSbs, foot. 



The Cephalopodous Molluscs are indeed highly organised for 

 Molluscs, for they possess in a high degree the sense of sight, hearing, 

 and touch. They appear with the earlier animals which present them- 

 selves on the earth, and they are numerous even now, although they 

 are far from playing the important part assigned to them in the early 

 ages of organic life upon our planet. The Ammonites and Belemnites 

 existed by thousands among the beings which peopled the seas during 

 the secondary epoch in the history of the globe. 



This great class is otherwise divided into two orders : Tentaculiferous 

 Ceplialopods, those furnished with strong fleshy tentacula, and Aceta- 

 luliferous, or sucker-bearing. 



TENTACULIFEROUS CEPHALOPODS. 



In place of bearing simple suckers (Acetabula), like the last order of 

 Cephalopods, this group is furnished with true organs of prehension, 



