98 NEW YORK STATE MUSEUM 
minute, averaging 2 millimeters in vertical length. They are scalenohedral 
in habit, the dominant form being the positive scalenohedron ¢: (17.15.32.2) 
im the! zone (10I121120]5 > Whis) is). aayaaaennny, instances, terminated by the 
planes of the negative rhombohedron &. (1012) in relatively small develop- 
ment. The scalenohedral faces are smooth and brilliant, yielding good 
reflections of the goniometer signal. Type I evidently marks an early 
stage of crystal deposition and corresponds genetically with the prismatic 
habit to be discussed under type II. The crystals occur in narrow seams 
in the limestone and are deposited directly on the wall rock. No instance 
of double termination was noted. 
Type II [pl. 15, fig. 2, 3]. Crystals presenting the two combinations 
of this type were noted on the same specimen which furnished type I. 
The combination shown in figure 2 is represented by small brilliant crystals 
of prismatic habit averaging 2 millimeters in vertical length. In the pris- 
matic zone the new dihexagonal prism v (5380) is present, developed to a 
considerable habit, the axial edges being beveled by narrow planes of the 
prism a(1120). All the planes in this zone are sharp and brilliant giving 
good reflections. In the rhombohedral zone the negative rhombohedron 
9. (0221) is a conspicuous form of this habit, the negative rhombohedrons 
¥. (0552) and &. (0551) are present in comparatively small development. 
Narrow planes of the positive rhombohedron p. (1011) truncate the polar 
edges of 9. furnishing excellent points of reference in the zone. The posi- 
tive scalenohedron :(15.13.28.2) in the zone [1011.1120] and close to 
t:(17.15.382.2) of type I is present as a series of well developed planes. The 
separate identity of these two forms which was at first a subject of doubt 
was satisfactorily established by a series of careful measurements of the 
polar angles for both forms, the measurements showing but little variation 
in either form. 
The rhombohedral-scalenohedral habit shown in figure 3 is referable 
to this type mainly on genetic grounds, the habit occurring in close asso- 
ciation with prismatic combination described above. The dominant form 
of this habit is the positive scalenohedron 0: (9.7.16.2) in the zone [1011.1120], 
