T R O C H U S. 97 



is tliat of a pointed cone, capable of standing 

 nearly perpendicularly, or but little inclined, upon 

 the flattened base of the last whorl : the aperture 

 broader than long, angular at the lower extremi- 

 ties of the columella, and at the carinate margin 

 of the outer lip, is so situated as to be nearly hori- 

 zontal when the shell is placed in an upright pos- 

 ture. From this most perfect structure, to the ver- 

 tical and circular formation, there are so many 

 gradations and varieties of aperture, that it were 

 endless to describe them. The most simple, though 

 not an unexceptionable, rule is, to consider all spe- 

 cimens as belonging to this genus which have any 

 angular tendency in the contour of the mouth, and 

 are, as to their general appearance, ^op-shaped, in 

 conformity with the meaning of their name, de- 

 rived from the Greek rgo^og. 



The remarkable faculty which the T. conchylio- 

 phorus possesses of attaching stones and testaceous 

 fragments to his shell, obviously during the period 

 of its formation, is not easily explained. We must 

 suppose, either that some very strongly adhesive 

 matter is combined with the calcareous secretions, 

 or that the animal is singulaa-ly tranquil in his dis- 

 position. H 



