CALIFORNIA ACADEMY OF SCIENCES. 13 



oo ( — 3 P 3) is determined by the zones a (2 P oc) : s (oo P) 

 and 2 (oo P 2) : c (P oo ). It is usually a very small face on the 

 edge a : s, and in one crystal only (Fig. 3, PI. I) attains con- 

 siderable size. It is also in the zone b ( — P) : m (oo P oo), 

 and in this zone was measured b : oo = 152° 33' (calculated 

 152° 33' 1"). 



fe> (3 P 3) (Fig. 10, PL III,) is a very small face in the zones 

 y (P) : o (2 P 2) and h (2 P oo) : s (oo P). It was found on one 

 crystal as a very small face on the edge h : s, and in another as 

 represented in Fig. 10, but with only one of its faces. It is one 

 of the rare forms. 



B (4 P 4) is still more rare, having been recognized but once 

 with certainty (Fig. 8, PL III). It is determined by the zones 

 y (P) : o (2 P 2) and t (oo P 2) : c (P oo). The latter zone was 

 proved on the goniometer. On the crystal represented in Fig. 

 10, PL III, the edge & : n is replaced by a very narrow face 

 (not drawn) that was so roughened that no reflection could be 

 obtained from it. It agrees in position with, and probably 

 is, B. 



k ( — 3 P 3) was found in three crystals, and is shown in Fig. 

 1, PL I, and Fig. 6, PL II. It is determined by the zones 

 c (P oo) : b ( — P) and b ( — P) : s (oo P) (on opposite sides of 

 the plane of symmetry). In the crystal shown in Fig. 6, PL II, 

 the faces were entirely dull, in the others very bright, giving 

 k : 6 = 157° 56' and 158° 0' (calculated 157° 56' 8"). 



Of the hemidomes, h (2 P oo) is the only one that attains con- 

 siderable size; the others are all very small. 



U (6 P oo) occurs as a small lozenge (Fig. 3, PL I.), when h 

 and ?i (oo P oo) are absent, and when the latter are present, as a 

 very narrow face on the edge n : h. It is usually accompanied 

 by W (4 P oo), developed in a similar manner but showing a 

 very marked tendency to curvature, which sometimes does and 

 sometimes does not involve also the face of U. In only one in- 

 stance could a satisfactory reading be obtained from W, giving 

 W : h = 159° 13' (159° 13' 50" calculated). 



h (2 P oo) I have already referred to as determining with g 

 (0 P), by enlargement or total disappearance, two somewhat 

 pronounced types. They are also moderately developed in forms 



