CEPHALOPODA. 339 



Thus we have at length been furnished with the proof of the di- 

 branchiate nature of the Belemnite, and we learn from the same 

 ocular evidence that it combined characters at present divided be- 

 tween three distinct genera of the order ; namely, first the calcareous * 

 internal chambered shell, to which the Sepia offers the nearest ap- 

 proach ; secondly, the formidable hooks of the arms, which charac- 

 terise the modern genus Onychoteuthis ; and, thirdly, the limited 

 attachment of the lateral fins to a position a little in advance of the 

 middle of the body, as in the Sepiola. 



The Belemnite, having the advantage of its dense but well-balanced 

 internal shell, must have exercised its power of swimming backwards 

 and forwards, which it possessed in common with the modern Decapod 

 Dibranchiata, with greater vigour and precision. Its position was 

 probably more commonly vertical than in its recent congeners. It 

 would rise swiftly and stealthily to infix its claws in the belly of a 

 supernatant fish, and then, perhaps, as swiftly dart down and drag 

 its prey to the bottom and devour it. We cannot doubt at least but 

 that, like the hooked Calamaries of the present seas, the ancient 

 Belemnites were the most formidable and predaceous of their class. 



LECTUKE XXIV. 



CEPHALOPODA. 



The deductions which were founded on the modifications of the 

 chambered siphoniferous shell and other enduring remains of the 

 very remarkable extinct genus which occupied our attention at the 

 close of the last lecture, obliged me frequently to refer to the type of 

 structure which characterises the Dihranchiate order of Cephalopods, 

 and which places these MoUusca not only at the head of that 

 division of the Animal Kingdom, but, in respect of its closer 

 proximity to the Vertebrate type, unquestionably at the head of the 

 whole Invertebrate series. 



The body of the Dibranchiate Cephalopod is divided, as in the 

 Nautilus, into two parts ; a head, containing the organs of sense, 

 mastication, and deglutition, and supporting the prehensile and prin- 

 cipal organs of locomotion, and a trunk or abdomen, consisting of a 

 muscular sac or mantle, with a transverse anterior aperture, and con- 

 taining the respiratory, generative, and digestive viscera. With one 



z 2 



