52 



UNIVALVES ^ NAUTILUS. 



so small as only to be defined by the microscope, a% liile 

 others, on the contrary, (especially some of the fossil spe- 

 cies), have been known to exceed two feet in diameter. 



Some species of this genus are found adhering to coral 

 rocks, the Siphunculus, for instance, is often brought 

 from the coral reefs, on the Sicilian shores. Among the 

 three or four fossil species, the Nautilus Helicites is wor- 

 thy of notice, as coming from St. Pfiter's Mountain, at 

 Maestricht. 



The Nautilus Belemnita or Thunder-stone, is also re- 

 markable, on account of its being considered by the vulgar 

 as a thunder- bolt, and only to be found after a storm. They 

 are found fossil in most parts of Europe, and when burnt 

 or rubbed smell like rasped horn. 



The American and Indian Oceans produce some of the 

 species of the Nautili, as also do the Mediterranean, Adri- 

 atic, and Red Seas; but by far the greater number are 

 found on the European and British coasts. Most of the 

 species are minute. 



