ITS MODIFICATIONS. 183 



The individuals of this class will differ from each 

 other in the inclination of M on M', and in the ratio 

 of the edge H to the edge D. 



Modifications. 



Class a. Obtuse solid angles replaced by single 

 planes. 



Class b. Obtuse solid angles replaced by two 

 planes. 



Class c. Acute solid angles replaced by single 

 planes. 



