TROCHUS. 
97 
is that 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 
The remarkable faculty which the T. condiylio- 
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 singularly tranquil 
in his disposition. 
H 
