I am trying to make a hermit crab shell, but am having trouble perfecting it. I have what is pictured below by using a helix defined by pitch and revolution with a variable pitch and just trying different numbers for the pitch and diameter. I think I should try implementing the golden spiral equation for this project. I am having trouble completing the spiral in the center top of the shell. I am also having trouble getting the spirals/revolutions to touch the one under it, you can see there is a gap in between the swirls in the picture below, but when I make the pitch any lower to try to close the gap, the loft feature does not work. What can I do here?

I don't think I want the shell to be a flat spiral, like in the following picture.