UNIVALVES. NAUTILUS. 7l 



otliers, 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 worthy of 

 notice, as coming from St. Peter's Mountain at Maes- 

 tricht. 



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. Mos^t of the 

 species are minute. 



NAUTILUS.-^Srt/Zor. 



A. Spiral, rounded, with contiguous whorls. 

 Pompilius {Gt. chamber d S,) *Crassulus. 

 *Calcar. *Lobatulus. 



*Crispus. *Carinatulus. 



*Beccarii, *Subarcuatulus. 



*L8evigatulus. Balthicus. 



*Depressulus. Helicites. 



*Umbilicatulus. Rugosus. 



Umbilicatus. 



B. Spiral, rounded, with separate whorls, 

 Spirula (Rants Horn.) Spcngleri. 

 Unguiculatus. 



