Please read in Nicolaides, the sections on cross contours and exercise 18, quick contour (p.75) and the five hour contour p. 74.
Keeping this reading in mind, I would like you to draw a shell (the spiraling kind) using the notion of contour and cross contour. The shell should fill a good portion of your paper and have monumental scale. Use your good sheet of paper, 36" X 42", and fill the page by using the zoom lenses in your minds eye.
This does not have to be a "blind contour," but rather a "contour study" using line - which moves over and around the form, describing the form the line travels over with enough accuracy OF TOUCH that a Martian could use it as a geological map and report back exactly the nature of the shell in question. Use cross contours wherever possible. A shell has a wonderful tracing of it's growth in the lines which circumscribe its surface. As if the wave and the snail formed it and gave you a good tracing of that formation.
You will see this spiral formation in much of nature, especially the human form, so learn it well - a study is an investigation which seeks to discover.
Materials are up to you. India ink or pencil, or charcoal and eraser.