Combinations of shells are useful and lend variety to the other shapes and forms. The number of combinations is practically unlimited so that only a few may be shown here. The first step will be to list all of the combinations previously described and indicate which types can be combined. The basic types of shells were previously classified as: 1) folded plates and domes, 2) barrel shells, 3) short shells, 4) domes of revolution, and 5) warped surfaces. The intersection shell has been omitted since it is really a combination. Warped surfaces do not combine very well with other types, particularly the folded plate so they will not be considered in combinations.

The combinations possible from the above list are: 1) barrel shells and folded plates, 2) barrel shells and short shells, 3) barrel shells and domes of revolution, 4) barrel shells and conoids, 5) folded plates and short shells, 6) folded plates and domes of revolution, 7) folded plates and conoids, 8) short shells and domes of revolution, 9) short shells and conoids, and 10) domes of revolution and conoids.