BASE, AND ITS MODIFICATIONS. 161 



Class u. Obtuse edges of the pyramid replaced by 

 two planes. 



Class v. Acute edges of the pyramid replaced by 

 tangent planes. / 



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. 

 Class x. Acute edges of the pyramid replaced by 



two planes. 



The new figures produced by class u, and or, would 

 be octahedrons, more obtuse than the primary, with 

 rhombic bases. 



Class 2/. Edges of the base replaced by tangent 

 planes. 



Planes y might be the lateral planes of a right 

 rhombic prism. 



