BASE, AND ITS MODIFICATIONS. 157 



Class o. Acute lateral solid angles replaced by 

 two planes, resting on the edges of the pyramids. 



If we suppose the octahedron to be placed with its 

 axis horizontally, the planes of classes 5, c, h, or o, 

 might be the lateral planes of right rhombic prisms. 



Class p. Acute lateral solid angles replaced by 

 two planes, resting on the edges of the base. 



Planes p might be the lateral planes of a right 

 rhombic prism. 



Class q. Acute lateral solid angles replaced by 

 four planes, resting on the primary planes, and inter- 

 secting those planes in lines parallel to the edges of 

 the pyramids. 



