SECTION Vlll. 



^57 



Plancus in his book de Conchis minus 

 notis littoris Ariminenfis, defcribes fome 

 recent minute kinds of this genus, which 

 he found in great quantities in the fea fedi- 

 ment, at Rimini in Italy. The Orthocerofes 

 he difcovered were fpecies fo very minute, 

 lefs than one quarter of an inch, and not 

 thicker than a pin, that they demanded 

 the aid of the microfcope, to difcern their 

 ftrudlure. Gualtieri, Tab. 19, has figured 

 four kinds of them, fent him by Plancus; 

 and Linn-cCus ranks them In his fyftem, as 

 Nautili *. 



How difFerent thefe are from thofe found 

 follil, is extremely ftriking ; the recent 

 fpecies are fo very minute, as to demand 

 the microfcope to view them ; the foflil 

 ones, on the contrary, are moftly very large, 

 frequently above a foot in length, and above 

 an inch and a half over, even the fmallefl 

 kinds ; as the Alveoli are feldom lefs than an 



"^Nautilus Orthccera, Linnaci, Syft.Nat, p. 1 164.289. 

 6 inch 



