Draw a shell quickly by using geometric shapes to rough out the form of the object. The first impression of a shell is that it is a simple curve, but closer inspection reveals intricate details in the ridges and grooves that are present. Find photos of shells or use real seashells as a starting point. When your work is finished, try adding shading or colour for a more realistic look. Shells come in a wide variety but for today, focus on a type of shell that is usually found in halves called the Van Hyning's Cockle.
Sketch a large wide oval. Sketch a smaller wide oval slightly overlapping the top of your first oval. The second oval should be about half the size of the first.
Define the shape of your shell, using the ovals as a rough guide. Smooth the intersection point between your shapes to help define the curved shape of the shell.
Draw vertical ridges on your shell. Finish the shape of the lip of the shell in a ruffled pattern that follows the ridges you have created.
Add horizontal grooves that curve around your shell.
Erase any extraneous lines.
Don't make the shape of your shell perfect. Many shells are irregular.