All of the basic forms have negatives of themselves. For example, the inside of a soup bowl is a negative sphere; the inside of an open box is a negative cube; a well is a negative vertical cylinder. The same rules about value shapes that apply to positive forms apply to negative forms.
The negative form of a sphere is a crater, in which we see crescents and ovals of light and dark just as we do in the positive form.
The negative cylinder is depicted with light to dark blends of parallel stripes.
The negative cone shape is depicted using adjacent triangular blends.