Several groups of siliceous microorganisms possess a skeletal latticework of interconnected rods. Skeletal configurations of one of these groups, the silicoflagellates, can be produced by a simple mathematical model that minimizes the apical surface area for a given basal area and internal volume. A simlar model that minimizes the total length of the skeletal elements, and thus the silica utilizationa and skeletal weight, produces configurations that area generally less common in silicoflagellates. The diversity of silicofalgellate skeletal morphologies suggests that both the minimization of apical surface area and the conservation of skeletal material may be important factors in skeletal design. The two most important morphologies found in modern oceans, the four-sided Dictyocha and the six-sided Distephanus, can co-occur in an environment where both factors have some relative importance. However, these models do not explain the range of silicoflagellate skeletal morphology found in nature.