of Crystalline Combinations. 419 
SQUARE-PYRAMIDAL SYSTEM. 
Relations of Edges, &c. 
An eight-sided prism with an eight-sided pyramid. 
E. C. horizontal. 
The faces of one eight-sided pyramid replace in pairs the principal terminal edges of 
the other pyramid. (S. T.) 
E. C. parallel to the edges replaced, and to each other, 
Half the number of faces of eight-sided pyramids, taken alternately. 
The faces may be corresponding ones at the two summits, or alternate ones. 
i 
Half the number of faces of four-sided pyramids taken, and alternately at the two 
summits. (h and h’.) 
And, of eight-sided pyramids, the faces corresponding to such faces of the four-sided 
ones. 
OBLONG-PYRAMIDAL SYSTEM. 
Relations of Edges, §c. 
A pyramid with its summit replaced by another pyramid. 
E. C. horizontal. 
