J56 C O N C H O L O G Y. 



pefts and other violent ragings of that im- 

 menfe niafs of waters ; and therefore the 

 Shells conftantly remain undifturbed in 

 them. 



Genus i. Orthoceros, fmiple ftreight 

 conical Shells, or no- wife turbinated ; and 

 gradually tapering from a broad end to a 

 fharp-pointed top, hke a ftrait horn, whence 

 their name. They are chambered from 

 bottom to top, and have a fiphuncuhis, or 

 pipe of communication, from chamber to 

 chamber. PI. II. fig. 12. is greatly mag- 

 nified, fig. 13. being the natural fize of 

 the Shell difcovered, — taken from Gual- 

 rieri. 



PI. IL fig. 14, is a fragment of a foflil, 

 orthoceratites, in a fmall fcale, taken from 

 Breynius de polythalamiis ; a a a a, the 

 cells or chambers ; b b b b^ the fiphuncu- 

 lus, or pipe of communicatipn, which 

 in both thefe figures is centraL 



Plancus 



