SECTION YilL i6i 



Cafts of ftone of this kind, for I have 

 never feen it In the Shell ftate, are found 

 in Dorfetfhire, France, and Switzerland^ 

 but never in any great degree of perfection* 



PL II. fig* II, is a Turbo Polythala- 

 mus, but by the miftake of the engraver, 

 the figure is laid flat ; whereas it (hould 

 have been ereft, in the farrie manner as a 

 Whelk, or other turbinated Shell. 



Genus 4* Gornua Ammonis, or Am- 

 monia, The Shells of this genus are per- 

 fe£l Helices^ the fpires lying between two 

 .flats or levels. PL II. fig. 20, is an Am-* 

 mollis, and fig. 21, is cut or opened, to 

 ihcw its feveral cells or chambers. 



The fpires are cylindric, and connefted 

 to each other. They gradually diminifh 

 or taper (on both levels equally alike) 

 from the circumference to the center ; fo 

 that by the gradual tapering of the fpires 

 to the center, the centers of both flats arc 

 concaves. 



M Th© 



