S66 PEARL NAUTILUS. 



course : and thus it pursues its voyage ; and if alarmed by any ap- 

 pearance of danger, takes in the water and descends." 



The paper nautilus is an inhabitant of the Mediterranean and At- 

 lantic seas. In the Indian seas is found a species so similar, that 

 it has generally been considered as a variety : it differs in having 

 the shell mr.rked into numerous slight tubercles on each side the 

 furrows. This is the variety described by Rumphius, in his ac- 

 count of its inhabiting animal, observed by him during his resi- 

 deuce at Amboyna. 



[Edit. Plin. Shaw. 



2. Pearl Nautilus. 



Nautilus Pompilius. Linn. 



This animal possesses a large and strong shell, often measuring 

 five or six inches in length : it is of a very firm or dense fabric, of a 

 shape somewhat compressed on the sides, with a very wide opening 

 or mouth, and with the back-part rolled into a spiral form within 

 the cavity of the shell. The colour, externally, is a dull yellowish- 

 white, marked with numerous zebra-like yellowish brown or dusky 

 bands ; and within, of the richest and brightest silvery-pearl-colour. 

 When the natural pellicle or epidermis of the outside is rubbed off, 

 the whole shell appears silvery also. The great and striking cha- 

 racter of the genus however, at least so far as regards the shell, is 

 the extraordinary structure of the internal part, which is formed into 

 a great number, (from thirty to forty) separate chambers or divi- 

 sions, each communicating with the rest by a small tubular hole 

 near the centre. The opening or mouth of the shell therefore pre- 

 sents a large but shallow concavity, pierced with a central or nearly 

 central hole, and beyond lie all the divisions before-mentioned. 

 The body or chief part of the inhabiting animal fills up the front 

 or great concavity, and that only ; while from its extremity pro- 

 ceeds a slender tail or process, passing through all the rest of the 

 chambers ; and it has been supposed by some, that the animal pos- 

 sesses the power of, at pleasure, filling up the chambers or cavities, 

 either with air or water, or of exhausting them of both occasion- 

 ally, in order to make itself specifically heavier or lighter, during its 

 navigations ; for this animal is also supposed to have a power of 

 sailing, though in a less perfect maimer than the argonaut, or paper 



