n8 C O N C H O X. O G Y. 



Helices (Helices) are thofe Shells that 

 have their whirls or tuniiiigs lying, as it 

 ^^ere, between two flats or levels, as feme 

 river fnails., poft-horn fiiails, ammonitae, 

 and others. See Pi. IL ng. 19, 22. PI. III. 

 fig. 19. 



Revolved Shells (univalvia tnrblnata, 

 clavicula intus recondita, vel ita in fe con* 

 torta, lit eoruni circumvolutiones nulla ex 

 parte promineant) are thofe that turn or 

 1 evolve withinfide, or whofe whirls or 

 turnings are hidden or abforbed within the 

 body of the Sheil, fo that only the outer 

 whirl is feen, and they have no clavicle; 

 fuch are the Nautili and the Cowries. See 

 PL II. fig. 16. Ph IIL fig. I, 2, 3, 4, 5. 



Winged Shells (Alatae) are thofe whofe 

 lips expand greatly outwards, and form 

 large flaps or wings ; as the Plough, the 

 Duck's Wing, the Spiders, and many 

 others. See Ph L fig. 6, 7, and PI. V. 

 4g.-i» Right- 



