11 



of the earth in which tliis Cephalopod was imbedded to favour the preser- 

 vation of the soft parts ; yet, from the very nature of the deposit in which it 

 was found, it must have become imbedded during a period of our planet^s 

 existence long antecedent to all human liistory and tradition. 



The fossil shells of the chambered Cephalopods, of wliich the Nautilus 

 and Spirula are the soKtary living remnants, are so peculiarly adapted to 

 dwelling in very deep water, that they seem to tell, by their very construc- 

 tion, of an age in wliich marme must have greatly more preponderated over 

 terrestrial space than at present ; as if, indeed, they had lived with the 

 gigantic Saurians in the midst of the waters, " before the progressive course 

 of the world, as we now see it, took its first departure^' ^. 



An extensive tribe of very minute chambered bodies called the Forami- 

 nifera was referred to tliis class until very recently, on account of the rela- 

 tion which they were thought to exliibit with the Nautilus shell ; and the 

 structure of the Spirula, on its discovery by Peron and Lesueur, was re- 

 garded as an undeniable proof of their cephalopodic nature. M. D'Orbigny 

 investigated their extraordinary varieties of formation with the most patient 

 ingenuity ; and divided them into upwards of fifty genera. " An important 

 service has been rendered to science by the discovery of the Spinda," said 

 Lamarck, and M. Deshayes, amongst others, exclaimed, " it is without con- 

 tradiction one of the most important facts with wliich science has been 

 enriched.^' It has, however, been fully demonstrated by M. Dujardin, on 

 the shores of the Mediterranean, that these many-shaped microscopic bodies 

 are notliing more than the cells of an inferior group of Zoophytes called 

 Ilkizopods.'\ 



The class of Cephalopods is divided by Mr. Owen and M. Deshayes into 

 two orders, according to the number of their brancliise or gills ; one group, 

 in which the Argonaut and Spirula occur, having only one pair of breathing 

 organs, DibrancJdataX, the other of which the Nautilus is the only living 

 example having two pairs, Tetrahranchiata^ . I shall not, however, avail 

 myself of this arrangement, because a difierence in the number of the 

 branchiae seems scarcely of sufficient importance to warrant the association 

 of the Spirula with the Argonaut, separate from the Nautilus. Lamarck 

 associated the Spirula with the Nautilus, separate from the Ai'gonaut, by 

 reason of their many-chambered shells, but a subsequent investigation of 

 the soft parts has shown that arrangement to be stiU more open to objection. 

 Are not these mollusks sufficiently distinct to constitute the types of tlu-ee 

 respective Orders ? The Argonaut has eight arms, each having two rows of 

 suckers, the shell being simply involuted and not chambered ; — the Spirula 

 has eight short arms, with minute promiscuous suckers, and two tentacles 

 with a club at the end, the shell being involuted, tubular, chambered, and 



* "WTiewell, Hist. Induct. Sci. t Deshayes, Anim. saus vert., vol. xi. p. 177. 



X Two-giJlcd. § Four-gilled. 



c 2 



