ITS MODIFICATIONS. 199 



Class b. Solid angles replaced by two planes. 

 The series of new figures would be contained 

 within 24 triangular planes. 



Class c. Terminal edges replaced by single planes. 



Produces a regular hexagonal pyramid on each 

 summit, resting on the planes of the prism. 



The new figures would be dodecahedrons with 

 isosceles triangular planes. 



Class d. Lateral edges replaced by tangent planes. 



Class e. Lateral edges replaced by two planes. 



The primary and secondary forms of this class, are 

 similar in character to some of the secondary forms 

 of the rhomboid ; and it is only by their respective 

 cleavages that they can be distinguished from each 

 other. 



