EXPLANATION OF TERMS. 225 



Rotatory. Like a wheel; from rota, awheel. 



Rostrated. Having a beak from rostrwra, a 

 beak. 



Refuse. Having the lower whorls of the spire 

 pressed into the body whorl, from re- 

 back, and tusws, beaten. 



Reversed. Applied to spiral shells, whose volu- 

 tions turn in the contrary direction to 

 the generality of shells, If when a shell is 

 placed on its base, with the front facing 

 the person looking at it, the aperture is 

 on the right side of the pillar, the shell is 

 said to be regular or dextral, if the aper- 

 ture is on the left side of the pillar, it is 

 said to be reversed or sinistral. 



Retractile. Capable of being drawn back ; from 

 re, back, and tract us, drawn. 



Reticulated. Crossed like net work ; from reti- 

 culww, a small net. 



Revolute. Rolled back ; from re, back, and 

 volutws, rolled. 



Rugose. Rough or wrinkled ; from ruga, a 

 wrinkle. 



Rufous. Of a reddish colour. 



Spire. The upper whorls collectively , from 

 the Greek a-ireip (speir), convolutions 

 gradually increasing in diameter. 



Suture. The circular line of the spire, where 

 one volution meets another ; from sutura, 

 a seam. 



Species. The subdivision of a genus, and dis- 

 tinguished from all others of the genus 

 Q 



