Nora,
 
Sexual dimorphism is very evident in some of the Strombidae.  The male
Lambis lambis is smaller then the female who has upward curved spines
and a much larger dorsal hump.  Similarly, the male Lambis chiragra is
half the size of the female.  I am also convinced there is an easily
discernible difference in the sexes of Strombus gigas, with the female
having a broad flaring lip and the male with a narrow lip that often
curves over the apex of the shell.  This last is not supported by
anything other than I've seen the two structures and just made a wild
jump to a conclusion.
 
Tom Eichhorst in New Mexico, USA