PRELTRTINARY OBSERVATIONS. 



xxi 



large that their sac Avould contain the body of an elephant. The flesh 

 of the sepia was esteemed a great luxury by the ancients. In Plate 

 VIII., fig. 1. is the sepia octopedia, an inhabitant of the British seas. 

 Fig. 2. is the beak of a species of sepia, the calmar ; these are found 

 fossil, and are called Rhyncolites. Fig. 3. is the nautilus pompilius 

 or pearly nautilus. Great uncertainty prevailed respecting the true 

 character of the nautilus, which has been removed by a scientific ex- 

 amination of the body of one of these animals caught by George Ben- 

 net, Esq., and of which an interesting account has been recently jmb- 

 lished by Mr. Richard Owen, illustrated by beautiful engravings. It 

 should appear from Mr. Owen's account, that the organization of this 

 animal is in many respects less perfect than that of several species of 

 sepia that have no external cell : it had ninety-two arms or tentacu- 

 lae. Fig. 3. is taken from Mr. Owen's first plate, but greatly redu- 

 ced ; it is chiefly intended to show the position of the animal in the 

 shell. It is a section representing the interior of the shell divided 

 into chambers, and the siphunculus passing through them. The nau- 

 tilus pompilius is not uncommon as a fossil shell. It may be seen 

 both recent and fossil in most museums. We shall now proceed to 

 notice the principal genera of chambered shells, not in the numerical 

 order of the plate, but as they approach the nearest to the form of the 

 nautilus.* 



The spiRULA (fig. 11.) is both a recent and a fossil shell : the turns 

 or whorls of the shell do not touch. The spirula is an inhabitant of 

 trophical seas ; the animal resembles that species of sepia called the 

 seiche or common sepia. The shell is almost entirely inclosed in the 

 sac. Indeed, it appears from its structure, that the animal could not 

 be contained within the outer cell.f 



The AMMONITE (fig. 6.) of which there are numerous species, dif- 

 fers greatly from the chambered nautilus, the whorls or turns being 

 all distinct, and in the same plane, and the cells are very small. The 

 siphunculus is placed near the outer edge of the shell. In many spe- 

 cies, the cells are divided by indented partitions, as represented in fig. 

 7. : in other species the cells are undulated. Some ammonites in the 

 vicinity of Bath are eighteen inches or more in diameter. The shell 

 must have been internal, and the animal that contained it very large. 

 Ammonites, though so abundant in the secondary strata, have not been 

 found in a recent state, except the account can be relied upon, of their 

 having been discovered in the Pacific Ocean. 



The scAPHiTE resembles an ammonite partly unrolled. A very re- 

 markable specimen of one recently discovered in France is represent- 

 ed fig. 4. It is not improbable, that many internal shells were com- 

 posed rather of a corneous substance than of shell, and were capable 

 of being coiled or folded by the will of the animal. 



Fig. 8. is a straight chambered shell called a baculite. 



Fig. 12., the orthoceratite, is a straight chambered shell resem- 

 bling ammonites unrolled, but the cells are divided by concave parti- 



* The animal that inhabits the thin open shell called the paper nautilus, but 

 more properly the argonauta, is also a species of sepia: it is common in the Medi- 

 leri'anean. It is very rarely found fossil. 



t According to, Lamarck, the animal, beside the eight arms of the sepia (see fig. 

 1. plate 8.), has two longer arms or feelers: in this respect it resembles the Calmar, 

 which is common on the coasts of Europe. 



