304 PROCEEDINGS OF THE AMERICAN ACADEMY. 



Referred to N3 this portion of the zone is somewhat incomplete and 

 contains the extra forms |, y, §, 4 3 and |. 



X- (0994). This rhombohedron is recorded by Bournon 38 from 

 Derbyshire and Cumberland. It was regarded by Zippe 39 as un- 

 certain. Figure 199 of Bournon suggests that the rhombohedron 

 determined by him as (0994) may possibly be (0552). The zone 

 [0994 -2ll0] contains only one unimportant scalenohedral form. The 

 form must be considered doubtful. 



F. (0-12-12-5). This rhombohedron was determined by Zippe 40 

 from a curved face without measurements. It was also found by 

 Sansoni 41 on crystals from Andreasberg, (Combination 189, Fig. 17). 

 Zonal relations suggest a somewhat higher degree of probability for 

 this form than for the preceding. 



^. (0552). This rhombohedron was also recorded from Andreas- 

 berg by Zippe. 42 In the combination in which it is shown (Fig. 90), 

 (0552) truncate the polar edges of (1231) in the negative sextants, a 

 zonal relation which seems highly rational. Furthermore, the form 

 falls in normal series N5 and marks the intersection of three well 

 defined zones. The form may be said to be well established. 



J. (0-13-13-4). This rhombohedron was observed by Rogers 43 



38 Bournon, C. de., London (1808). 



39 Zippe, loc. cit. 



40 Zippe, loc. cit. 



41 Sansoni, loc. cit. 



42 Zippe, loc. cit. 



43 Rogers, A. F., S. of M. Quar., 23 (1902). 



