118 BULLETIN OF THE UNIVERSITY OF WISCONSIN. 



r, R (1011). 



e, —m (0112). 

 V, Rs (2131). 



a, —MR (0.11.11.20).* 



b, — IIR (0.18.18.25).* 

 /, — 2R (0221). 



c, 24R (24.0.24.1).* 

 8, lOR (10.0.10.1). 

 Ic, IR (5052). 



53,' tR2 (1123). 

 t, }R3 (2134). 

 67,' iRi (5279). 

 £, iRI (4156). 



These forms have been determined by the following 

 measurements which are for the most part averages of 

 several readings made on corresponding angles" : 



1 Numbers used by Irby. 



2 The vicinal character of r prevented measurement, but the plane is easily identified by 

 the cleavage. The face k is determined by its zones. 



