TABLE NUMBER 1 733 



With a singular 6-fold axis — Dihexagonal Bipyramidal Class or 

 Normal Group, Hexagonal System. 



With a singular 4-fold axis — Ditetragonal Bipyramidal Class or 

 Normal Group, Tetragonal System. 



With three singular 2-fold axes perpendicular to each other — 

 Orthorhombic Bipyramidal Class or Normal Group, Ortho- 

 rhombic System. 

 JifWith a singular 3-fold axis and no plane of symmetry perpen- 

 dicular to it — Ditrigonal Scalenohedral Class or Rhombohedral 

 Group, Hexagonal (Trigonal) System. 

 ### With no singular axes, but with three like axes perpendicular to 

 each other. 



Perpendicular axes 4-fold — Hexoctahedral Class or Normal 

 Group, Isometric System. 



Perpendicular axes 2-fold — Dyakisdodecahedral Class or Pyrito- 

 hedral Group, Isometric System. 



2. With no planes of symmetry: 



(a) With a singular 3-fold axis of symmetry — Trigonal Rhombohedral 



Class or Trirhombohedral Group, Hexagonal (Trigonal) Sys- 

 tem. 



(b) With no axis of symmetry other than one-fold — Triclinic Pinacoidal 



Class or Normal Group, Triclinic System. 



B. WITHOUT CENTER OF SYMMETRY 



1. With one or more planes of symmetry: 



(a) With no or but one axis having a period greater than one- fold. 

 # Opposite ends of crystals unlike (axis polar). 



Polar axis 6-fold — ^Dihexagonal Pyramidal Class or Hemimorphic 



Group, Hexagonal System. 

 Polar axis 4-fold — Ditetragonal Pyramidal Class or Hemimorphic 



Group, Tetragonal System. 

 Polar axis 3-fold— -Ditrigonal Pyramidal Class or Rhombohedral 



Hemimorphic Group, Hexagonal (Trigonal) System. 

 Polar axis 2-fold — Orthorhombic Pyramidal Class or Hemimor- 

 phic Group, Orthorhombic System. 

 Polar axis 1-fold — Monoclinic Domatic Class or Clinohedral 

 Group, Monoclinic System. 

 ## Opposite ends of crystals like (axis not polar) — Trigonal Bipy- 

 ramidal Class or (Trigonal Pyramidal) Group, Hexagonal 

 (Trigonal) System. 

 (6) With more than one axis having a period greater than one-fold and 

 more than one plane of symmetry (some of the axes may join 

 the mid-points of opposite edges). 

 With a singular 3-fold axis and a plane of symmetry perpendicular 

 to it — Ditrigonal Bipyramidal Class or Trigonotype Group, 

 Hexagonal (Trigonal) System. 

 With a singular 2-fold axis and no plane of symmetry perpendicular 

 to it — Tetragonal Scalenohedral Class or Sphenoidal Group, 

 Tetragonal System. 

 LI — Bull. Geol. Soc. Am., Vol. 21, 1909 



