CALCITES OF NEW YORK 99 
a form related in series to +: of type I, which is present as a series of bright, 
well developed planes giving good reflections. In the rhombohedral zone 
the rhombohedrons ¢.(0221), ¥. (0552) and p. (1011) noted on the pris- 
matic habit are present, the two latter developed to a rather more consider- 
able habit. The positive rhombohedron m. (4041) is here present as a 
series of small bright faces. Small, well developed planes of the negative 
scalenohedron 1: (3581) in the zone [1120.0221] are present, modifying the 
acute polar edges of 9:. On the whole the combinations of types I and II 
appear to be more closely interrelated than those of the succeeding types 
and may almost be considered as representing a single genetic phase. 
Type III [pl. 15, fig. 4]. The crystals of type III are in general 
larger than those of the preceding types, averaging 15 millimeters in vertical 
length, and occur in close parallel aggregates. They are characterized by 
a decided tendency to formation of vicinal planes specially in the rhombo- 
hedral zone where a vicinal series of planes marks the passage from the 
negative rhombohedron ¢.(0221) to the prism b(1010). Both of these 
forms are somewhat ill defined and were noted in the limits of the above 
series. The positive scalenohedron 8: (8.4.12.1) is present as a series of 
well developed planes of fair brilliancy. The positive scalenohedron 
P: (3251) in the zone [1011.1120] and the negative scalenohedron tr: (3581) 
in the zone [1120.0221] are present as well developed forms giving fair 
reflections. Crystals of this type although of a later generation than those 
of type II retain the steep rhombohedral habit entirely lacking in type IV 
and appear in a measure to link together the two generations of calcite 
crystals of this occurrence. 
Type IV [pl. 15, fig. 5,6]. The crystals of this type are in size and 
number by far the most prominent of the occurrence, particularly with 
respect to the rhombohedral habit shown in figure 6. Crystals of this latter 
habit occur on all the specimens comprising the suite and in some instances 
attain a diameter of 8 centimeters. In general the type is distinguished by 
the prominence of the negative rhombohedron 3. (0112), a form absent 
from the three preceding types, and by the presence of the prisms a (1120) 
and b(1010) in considerable development. 
