348 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



g' (21 -8 -29 -5) = (55-8-32). This scalenohedron was noted by 

 Flink 146 on crystals from Langban, Sweden. As shown by the figure 

 cited, the observed planes lie in zone [5051 : 0- 10- TO- 1] the form (5051) 

 being present on the combination. The zonal relations of this form 

 in general are not good_and it is to be_ noted that the hypothetical 

 scalenohedron_ (25 • 10 • 35 • 6) = (22-3-13) which is also in the zone 

 [5051 : 0-10- 10-1] has simpler Miller indices, better general zonal 

 relations and differs from (21-8-29-5) in value of the <p angle by 35', 

 the p angles corresponding to within 2'. The hypothetical scaleno- 

 hedron (25-10-35-6) is a possible substitution. 



Negative Scalenohedrons not Previously Included. 



T (6-8-14-3) = (23-5-19). This scalenohedron was recorded by 

 Sansoni 147 on crystals from Andreasberg. The form marks the inter- 

 section of a number of well marked zones and should be classed as 

 probable 



r (4-9-13-6) = (23-11-16). This scalenohedron was observed by 

 Schnoor 148 on crystals from Neumark, Sweden. Although not 

 presenting as good zonal relations as the preceding form, this scaleno- 

 hedron marks thejntersection of the zones [0332 : lOlO], [OlTl : 4592] 

 and [0553 : 13-0-13-2). The form should be classed as probable. 



f (2-20-22-21) = (15-13-7). This scalenohedron was observed 

 by Cesaro 149 on crystals from Rhisnes, Belgium, and the indices 

 (2 -20 -22 -21) substituted for (2 -19 -21" -20) = (43-37-20) given in a 

 former paper on the same occurrence. Cesaro points out the fact that 

 the form_(2-20-22-_21) lies at the intersection of the zones [OlTl : 

 2110], [4483 : 17-8-25-3] and [4047 : 0887]. This would seemjto be a 

 good zonal relation, the form, however, lies quite close to (0111) and 

 may possibly be vicinal to the rhombohedron. It is somewhat doubt- 

 ful. 



C (4-20-24-17) = (15-11-9). This scalenohedron was noted by 

 Sansoni 15 ° on crystals from Uto, Sweden. The form was observed 

 in combination w'th (0887) thus emphasizing the zone [0887 : 6281], 



146 Flink, Arkiv. f. Kemi. Min. Geol., 3, Fig. 156 (1910). 



147 Sansoni, F., loc. cit., Fig. 10. 



148 Schnoor, loc. cit. 



149 Cesaro, loc. cit. 



150 Sansoni, F., Giorn. d. Min., 1 (2), 129 (1890). 



