60 CATECHISM OF CONCHOLOGY. 



aperture, or one inclining to ovate, and that the 

 Trochus has an angular one. This peculiarity 

 ought sufficiently to characterize the different 

 genera, and it will be found almost universally to 

 hold good. 



Q. What is the form of the shell? 



A. A spiral.' The name of this genus is as 

 closely connected with that of its predecessor, 

 as are the individuals which severally compose 

 them ; Turbo signifying, like Trochus, any thing 

 that whirls round ; a top. Both genera are found 

 among the rocks on craggy shores, and on the 

 sand, after a storm has detached them from their 

 accustomed refuge. 



Q. Are not the shells of this genus very 

 beautiful ? 



A. They are generally solid, ponderous, shin- 

 ing, and often elegantly variegated. A large 

 and beautiful specimen, in the possession of Mr. 

 Bullock, was valued at two hundred guineas. 



CHAP. XXXII. 



UNIVALVES: 

 HELIX; Snail, or Spiral. 



Q. DOES the Helix differ considerably from 

 the Turbo? 



