346 PROCEEDINGS OF THE AMERICAN ACADEMY. 



tions hold good for the form (10 • 5 • 15 • 4) . The form should be classed 

 as quite probable. 



P (13-7-20-3) = (12-1- 8). This scalenohedron was observed by 

 Palache 138 on one crystal from the Lake Superior region. The form 

 corresponds to relatively simple indices and lies at the intersection 

 of a number of well marked zones. The form may be regarded as 

 well established. 



<£ (17-8-25-3) = (15-2-I0). This scalenohedron was observed 

 by Cesaro 139 on a number of crystals from Rhisnes. The form was 

 determined from a number of good measurements, and presents excel- 

 lent zonal relations. It may be regarded as well established. 



n (63-28-91-11) = (55-8-36). This scalenohedron was observed 

 by Melczer 140 on crystals from the vicinity of Budapest. The pole 

 of this form does not fall in any well marked zone and lies quite close to 

 that of (17-8-25-3). Again, the hypothetical scalenohedron (23-10- 

 33-4) = (20-3-13) lies sufficiently close to (63-28-91-11) to be well 

 within the limits of good measurements, thus: 



From this it would appear that either (17-8-25-3) or (23-10-33-4), 

 both of which have more rational indices and better zonal relations, 

 could be substituted for (63-28-91-11). 



A (70-21-91-13) = (58-13-33). This scalenohedron was observed 

 by Sansoni U1 on two incomplete crystals from Andreasberg. The 

 somewhat irrational indices assigned to this form by Sansoni were 

 evidently derived from the mean values of the measured angles by 

 an emperical application of the derivation formulas. The form does 

 not present good zonal relations and was suspected of being vicinal 

 to (6281). The form is rather doubtful. 



U (6171) = (14-4-7). This scalenohedron was recorded by Butt- 

 genbach. 142 The form presents excellent zonal relations and_ falls 

 in normal series N3 in the zone developed between [2131 : 1010] = 

 [201 : 211]. It should be classed as probable. 



138 Palache, C, loc. cit., Fig. 7. 



139 Cesaro, G., loc. cit. 



140 Melczer, G., Fold. Kozlony, 26, 79 (1896). 

 HI Sansoni, F., Atti. d. Lincei Mem., 14 (1884). 



142 Buttgenbach, H., Soc. Geol. Belg. Ann., 32, 86 (1905). 



