14 MOLLUSCA. 



extremity of the shell — this column is termed the siphon. The turns 

 of the spire do not come into contact. 



But a single species, Nautilus spirula, L. ; List., 550, 2, is 

 known. The 



Nautilus, properly so called. 



Has a shell which differs from the Spirula in the sudden crossing 

 of the laminae, and in the last turns of the spire, which not only touch 

 the preceding ones but envelope them. The siphon occupies the 

 centre of each septum. 



N.pompilius,h. ; List. 551, the most common species; it is 

 very large, formed internally of a beautiful mother-of-pearl, and 

 covered externally with a white crust varied with fawn-coloured 

 bands or stroaks(a). 



The animal, according to Rumphius, is partly contained within 

 the last cell, has the f>ac, eyes, jjarrot-beak, and funnel of the 

 other Cephalopoda; lut its mouth, instead of having their large 

 feet and arms, is surrounded by several circles of numerous 

 small tentacula without cups. A ligament arising from the back 

 traverses the whole siphon and fastens it there*. It is also 

 probable that the epidermis is extended over the outside of the 

 shell, though we may presume it is very thin over the parts that 

 are coloured. 



Individuals are sometimes found, — Naut. ponpilius, S, Gmel.; 

 List., 552 ; Ammonie, Montf., 74, in which the last Avhorl does 

 not envelope and conceal the others, but where all of them, 

 though in contact, are exposed, a circumstance which approxi- 

 mates them to the Ammonites ; they so closely resemble the 

 common species, however, in all the rest of the shell, that it is 

 scarcely possible to believe them to be any thing more than a 

 variety of it. 



Fossil Nautili are found of a large or moderate size, and 



much more various, as to form, than those now taken in the 



oceanf. 



Chambered shells are also found among fossils, furnished with 



simple septa and a siphon, the body of which, at first arcuated, or 



even spirally convoluted, remains straight in the more recent parts ; 



they are the Lihius of Breyn, in which the whorls are sometimes 



contiguous^, and sometimes distinct — the Hortoles oi Montfort. 



* The figiire of Rumphius is absolutely unintelligible, and it is somewhat asto- 

 nishing, that, of the many naturalists who have visited the Indian Ocean, not one has 

 ever examined or collected this curious animal, which belongs to so common a shell. 



t Large species, with a sinple siphon: the Angdlite, Mont., f. 1, 6;— the 

 Aganide, Id., 50 ; — the Cantrope, Id., 46. 



1 Nautilus lituus, Gni. : — yuut. semilituus, Plane., I, x. 



{C^ (o) See a very beautiful illustration of a specimen of Nautilus, by Richard 

 Owen, Esq. — ExG. Ed. 



