334 PROCEEDINGS OF THE AMERICAN ACADEMY. 



2° The number of forms included in the zone. 



3° The number of forms not previously discussed which are in- 

 cluded in the zone. 



Accepting these conditions we pass to the discussion of these supple- 

 mentary zones. 



Scalenohedrons OF the Zone [2021 : 0221 : 1010] = 

 [115:111:211]. Symbol |. 



In the portion of this zone between (2021) and (0221), an obvious 

 knot occurs at (3142) = (30l) which is also a knot point of zone 4. 

 4. Developing the fragment between (30l) and (111) we have: 



<P_ 



111 



1 



Referred to N3 this zone fragment is very incomplete and contains 

 the extra forms ^ and j^. | falls in normal series N4. 



f (6 -20 -26 -13) = (15 -9 -IT). This scalenohedron was observed by 

 Palache 106 on three crystals from the Lake Superior region of Michigan. 

 On the combination cited it occurs developed to a considerable habit 

 combined with (1453) and (4-20-24-17), the three scalenohedrons 

 lying in zone. This fact taken in conjunction with the perfect qual- 

 ity of the faces leaves little question as to the probability of the form. 



V (2-8-10-5) = (17-11-13). This scalenohedron was observed by 

 Sansoni 107 on two crystals from Andreasberg. The form as measured 

 by Sansoni agrees well with theory and marks the intersection of the 

 zones [0665 : 1120] and [2025 : 0110]. It should be regarded as fairly 

 probable. 



In the portion of the zone between (0221) and (1010) the principal 

 zone intersection occurs at (3251) = (302) which developed as a knot 



106 Palache, C, loc. cit., Plate XIV, Fig. 16. 



107 Sansoni, F., loc. cit., Plate III, Fig. 25. 



