Feb. igoo. Crystal Forms of Calcitk -Farrington. 241 



rence, appearing sometimes as a single plane, more often as two, and 

 only once in its full number of three planes. 



In conclusion, the following list includes the forms noted on the 

 Joplin calcites by the writer : 



r t ion,+£ n, 4153, 1 1 +R| 



J/, 4041, +i.ff t/,2iji, i 8 +/?3 



w, 3145. V 



'.on 2 -;./v' /,2i34, J« +|7? 2 



/. 0443 -I* 

 ^.0/75 I* -f}A>3 



f, 0221 -2 A* 



9,0441 4 A' 

 2?, 0.1 1.1 1.1, -1 1 A' 

 .Q, 1. 20.20. 1, -20 A' 



It is evident that the largest variety of forms occurs in the zone 

 of negative rhombohedrons. Indeed, it is hardly likely that the 

 above list includes all the negative rhombohedrons which occur, as 

 several measurements made by the writer indicated others, although 

 they could not positively be identified. The positive rhombohedrons 

 are of rare occurrence and have little to do with determining the 

 forms of the crystals. Among the scalenohedrons, v, + R3, is almost 

 universally present and is usually the dominating form. This 

 scalenohedron in connection with e, -| R, and/, -2R, determines the 

 habit of most of the Joplin crystals. 



