Fes. 1900. CrystaL Forms or CALcirE —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: 
7, 1011, +R M, 4153, 18 TRS 
M, 4041, +4R Worst, +R3 
Ww, 3145, 3? 
é, O112 -;R t, 2134, 3° +3h2 
7,0445 -4R 
IT, 0775 -ZR +423 
J, 0221 -2R 
m,0441 -4R 
2S, O.1L.11.1, -11R 
O%.F,20-20.1, -20R 
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, v7, + 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, 
