UNIVALVES. NAUTILUS. 71 



Some species of this genus are found adhering to coral 

 rocks; the N. siphunculus is often found on the coral reefs 

 on the SiciHan shores. 



Of the fossil species, the N. helicites and N. belemnita 

 are worthy of notice, the former as coming from St. Pe- 

 ter's Mountain at Maestricht; and the latter from the po- 

 pular belief of its t)eing a thunderbolt, and only to be met 

 with after a storm. The N. belemnita is found in most 

 parts of Europe, and, when burnt or rubbed, smells like 

 rasped horn. 



The American and Indian oceans, and the Mediterra- 

 nean, Adriatic, and Red seas, produce some of the species 

 of the Nautili ; but by far the greater number are found 

 on the British, and most of the European coasts. 



NAUTILUS.— ^yatVor. 



A. — Spiral, rounded, with contiguous whirls. 



Pompilius — Great-chambered. *Crassulus — Strong. 

 *Calcar — Spur. *Lobatulus — Lohed. 



*Crispus — Keel-edged. *Carinatulus — Keeled. 



*Beccarii — Beccaria^s *Subarcuatulus — Suharcuated. 



*Lsevigatulus — Smooth. Balthicus — Baltic. 



*Depressulus — Compressed. Helicites — Fossil. 



*Umbilicatulus — Umhilicated. Rugosus — Rugged. 

 Umbilicatus — Oblique jointed. 



B. — Spiral, rounded, with separate whirls. 



Spinxla — Ram's-horn. Spengleri — Spengler^s. 



Unguiculatus — Nail-shaped. 



