330 PROCEEDINGS OF THE AMERICAN ACADEMY. 



9?: (5 -10 -15 -4) = (837). This scalenohedron was observed by 

 Sansoni 102 on crystals from Andreasberg. Although the angles 

 measured by Sansoni do not agree very well with theory, the form 

 marks the intersection of the zone [0554 : 1120], a relation which was 

 noted by Sansoni. The form moreover, falls in normal series N4. 

 It should be ranked as probable. 



Hypothetical scaleiiohedrons. In the above series the missing term 

 2 corresponds to the hypothetical scalenohedron (2- 11-13 -3) = (647). 

 This form marks the intersection of the zones [2023 : OlTO], [0331 : 

 1120] and [0441 : 8081] all of which are marked by rational and well 

 established forms. The form should be retained as hypothetical. 



In the portion of the zone included between (0551) = (223) and 

 (1120) = (101) the following forms have been recorded: 



a 



lOl 

 1 



Referred to N2 this portion of the zone is complete and contains no 

 extra forms. 



Zone 12 = Z i2 . — Scalenohedrons of the Zone [0554 : 5052]. 



This zone contains only one scalenohedron which has not already 

 been discussed in the analysis of the preceding zones, namely : 



3S (7 -4 -II -6) = (813). This scalenohedron was observed by 

 Palache 103 on crystals from the Lake Superior region of Michigan. 

 On the combination figured by Palache, the form occurs with (20- 11 • 

 31-15) and (37-19-56-21) in a zone extending from [1123 : 2131] = 

 [f P2 : Pi3]_not [R : R3] as stated by Palache. The form also falls in 

 zones [0223 : 1010] and [4153 : 0331]. It may be regarded as well 

 established. 



102 Sansoni, F., Accad. d. Line. Mem. 19 (1884). 



103 Palache, C, Geol. Surv. Mich., 6, Plate XII, Fig. 5 (1900). 



