Step 1:
Prefold over these two lines.

The pearls are small paper balls......      Done!

Step 8:
Valley-fold over 4 edges in once, do the same on the other side

Step 6:
Make zig-zag folds into the right direction, all lines are already prefolded

Step 13:
Now the model looks like this.

Step 12:
Press the corners inwards with your finger by making an inside reverse fold on each corner.
Do the same on the left.

Step 11:
Fold over these four sets of two lines, the mountain-folds are already prefolded.

Step 10:
Mountain-fold over these four lines.

Step 9:
Mountain-fold over these four lines.

Step 5:
Unfold the model.

Step 7:
Hold the center of the model between your fingers

Step 3:
Valley-fold over these two lines.

Step 2:
Valley-fold over these two lines.

Step 4:
Valley-fold over these two lines.

Step 15:
Fold the model in half.

Step 14:
Make an inside reverse fold on each edge you've made in step 12.

This is a DIY-video tutorial for folding the seashell:

If you want, you can make decorative Origami pearls for the seashells