82 UNIVALVES NAUTILUS. 



The Nautili differ exceedingly in size; some are so 

 small that they can only be defined by the microscope, 

 while others are nearly a foot in diameter. 



The N. scrobiculatus is the most rare species of this 

 "■enus. 



Some species of the Nautilus are found adhering to co- 

 ral rocks, particularly the N. siphunculus, which is often 

 brought from the coral reefs on the Sicilian shores. 

 The American and Indian Oceans, as well as the Me- 

 diten'anean, Adriatic, and Red Seas, produce species of 

 Nautili ; but the greater number are found on the Eu- 

 ropean and British coasts. The species from the last 

 mentioned locality are minute. 



This and the preceding genus, from a similarity in 

 form, were originally included under the same generic 

 name NawriXoc, (sailor), so called by the early naturalists, 

 from the nautical skill which the animal of the Argo- 

 nauta was supposed to exert in directing its fragile bark. 

 The great difference in internal structure induced sub- 

 sequent conchologists to separate the genera. 



In the following enumeration of the species of the 

 sfenus, we have omitted the names of those which we 

 have not found figured in any author. They are, with 

 few exceptions, microscopic shells. 



Division I. — Spiral, with eontig'uous whorls. 



ScieiUiJic Name. Locality. Common, Name. 



Pompilius Africa, Amboyna, Cliina, 



India Gt, chambered N. 



Scrobiculatus. • • < New Guinea Sunken spiredo • • 



Lacustris Kent, Denmark • • • Lake do • • 



