PLATE XC. 



Some specimens are pure white, others beautifully tinged with 

 purple ; and the most perfect white and brown. The mouth is round, 

 surrounded on the outside by a thick prominent border. It has no 

 umbilicus. The shell consists of five spires, gradually tapering to an 

 acute point ; and separated by a depression. The longitudinal ribs 

 are thick and prominent. 



