i68 C N C H O L O G Y. 



the body ; and all the other fpires are very 

 fmall, and taper into a concavity, fo that 

 the center is deeply hollowed or umbili^ 

 cated. Pi. II. fig. 15, an Ammonoides, 

 Thefe elegant foffils are found at Draycot 

 in Wiitfhire, and in Switzerland, 



Genus 6. Nautilus,. The Nautili I de- 

 fine to be revolved Shells, or fuch whofe 

 fpires never appear externally, but lie la- 

 tent or quite hidden within the body of the 

 Shell. Turbinata, volutin apice non emi^ 

 pente : vel clavicuia intus recondita. 



The Nautili are of a chambered (truflure; 

 the pai-titions of the cells or chambers being 

 concavo-convex roundifh plates. How- 

 ever, I have feen foffil kinds with folia- 

 ceous futures like the Ammonite ; which 

 implies, that all the fpecies have not fuch 

 regular roundifh partitions : and, indeed, 

 Breynius folely, on this account, divides 

 the Nautili into two orders, of thofe w^ith 

 concavo-convex femilunar diaphragms, and 

 jihofe with jagged or finuated diaphragms. 



PI. II, 



