58 CATECHISM OF CONCHOLOGY. 



attribute of imperial dignity, was anciently pro- 

 duced from the Murex. 



A. It was ho ; but the purpurae of the ancients 

 was not, however, confined to this one family of 

 Testacae, but certain species of Buccinum and 

 other shell-fish also furnished it. 



Ancient Lyrian coins sometimes bear the Mu- 

 rex and Buccinum, in commemoration of the 

 Tyrian purple. 



Q. Where are they generally found ? 



A. In almost every part of the world ; they 

 still constitute the chief riches of Nicoya, 



" Swains on the coast the far-fam'd fish descry, 

 That gives the fleecy robe the Tyrian dye." 



CHAP. XXX, 



UNIVALVES: 

 TROCHUSJ Top Shell. 



Q. How am I to distinguish the Trochus? 



A. By observing that the shell is spiral, and 

 more or less conic; that the aperture is Jour- 

 sided, and somewhat angular, or more round, 

 having the upper side transverse and contracted, 

 and the pillar placed obliquely. 



Q. Is it not very difficult to distinguish the 

 Trochi from the Turbines ? 



