On two special classes of parallelohedra in E⁶

The cone of positive-definite quadratic forms is subdivided into aggregates of parallelohedra having certain properties. In E⁶, the Σ-subcones are investigated and, in particular, the Σ₀-subcone will be described which first occurs in E⁶ and which is governed by the group . Further the -subcone which is governed by the group will be discussed for d = 6.