40 



POPULAR CONCHOLOGY. 



nearly of the same specific gravity as the surrounding 

 water, and enables it to rise to the surface of the sea, or 

 sink to the bottom, simply by altering the extent of the 

 surface exposed to the water by its soft parts."* They 

 usually remain in the depths of the sea, and are able to 

 creep along rather quickly, supporting themselves upon 

 their tentacula, with the head downwards, and the shell 

 raised above ; they often get into the fishermen's nets 

 when thus moving about at the bottom of the sea. After 

 stormy weather, as it becomes more calm, they may be 

 observed in great numbers, floating upon the surface of 

 the waves, with the head put out, and the tentacula resting 

 upon the water, the shell at the same time being under- 

 most ; they do not, in a general way, remain long floating 

 in this manner, and have the power of easily returning to 

 their favourite situation at the bottom of the sea, by merely 

 drawing in their tentacula and upsetting the shell, which 

 immediately sinks with them. It was only in 1829 that 

 this animal was known with any certainty, one having 

 been caught alive, by Mr. Gr. Bennett, near the New 

 Hebrides Islands ; the animal, after drawings were made 

 of it, was preserved in spirits, and is now in the museum 

 of the College of Surgeons. 



" Certain it is that the Nautilus, in its floating position, 

 has neither arms capable of rowing, nor membranes adapted 

 for sailing," f as so often described by the poets. 



The ancients fabricated drinking-cups of the shells of 

 the Nautilus Pompilius ; another species, N. umbilicatus, is 

 very rare, and is distinguished by a large umbilicus on each 

 side ; those found in a fossil state are of various sizes ; 

 most of them beautifully represented in " Sowerby's Mi- 

 neral Conchology." 



Man tell. 



t Reeve. 



