Well, Everyone!

Here I am again working on some of the shells in that same
old collection our club bought.  I have Kevin Lamprell's
book on Spondylus and am trying to i.d. them (most have a
label, but they are innacurate).

I keep encountering the erm "gibbous" to refer to the
shell shape.  Will someone explain this term to me,
please?

Thanks,
linda