100 



N. spirula; and the circumstance of the Argonaut a being inhabited by a 

 mollusca of this class, leave but little doubt that all these shells have 

 been the solid appendages of similar animals. 



The representation given by Rumphius,d'AmboimcheRar. Tab. 17, Fig.c. 

 of the dead animal of the N. pompilius, al though />f an animal which was 

 much injured, not only gives the idea of a similar animal, and shows the 

 appendage by which it was connected with the siphunculus of the shell ; 

 but also seems to bear that figure which authorizes the supposition, that 

 part of the shell had been let into the body of the animal. This partial 

 envelopement of the shell by the animal is also confirmed, as is justly 

 observed by Lamarck, by the blanched appearance, which extends 

 some little distance from the edge of the mouth of the shell of the 

 N. pompilius, and which differs so widely from that which is yielded by 

 the other external part of the shell, wtiich is beautifully marked by 

 transverse orange-coloured stripes. 



LXXII. Nautilus. A spiral, many-chambered, discoidal univalve, 

 with smooth sides. The turns contiguous, the outer side covering 

 the inner. The chambers separated by transverse septa, which are con* 

 cave outwards, and perforated by a tube passing through the disk. 



The different chambers of these shells are very shallow, when com- 

 pared with the last, which forms the opening, and which is, doubtless, 

 the residence of the animal. 



Whilst examining these shells, it is necessary to pay particular atten* 

 tion to that particular organization, by which a communication is kept 

 up between the animal and the most interior part of the shell ; since we 

 shall not otherwise be able to judge of the peculiar modifications of these 

 parts, which occur in the fossil remains of this and of other genera of 

 this family. 



Some have supposed the siphuncle of the nautilus to have been a 

 rigid testaceous tube : thus M. Bosc says : " Toutes ces cloisons sont 

 traversees par un petit tuyau cylindrique, epais, creux, imperfore late- 

 ralement, qui paroit composoit de petits tuyaux plus evases d'un cote, et 



