VOL. I. PLATE XII. 



FIG. 57. - 8 ^ P ) m ) {",}. A right six-sided 

 r 2 



trapezohedron. 

 FIG. 58. - 2 (( F ) m ) &\. A left six-sided tra- 



pezohedron. 



FIG. 59. Rhombohedral combination. 



R -1. (P 2) 5 . R. |R. R + l. (P) 3 . R+ QD- 

 a b c d e f g 



FIG. 60. Di-rhombohedral combination. 



R oo. P. 2 (R). P -}- 1. P + QD. 

 a b c d e 



p 



FIG. 61. . A hemi-pyramidal form, analo- 



Rj 



gous to the tetrahedron. 



p 

 FIG. 62. _. The same, in inverse position. 



