CALCITES OF NEW YORK 65 
Type IV [pl. 4, fig. 1]. Crystals of this type are, in general, larger 
than those of types II and III, crystal 4, which was the largest one meas- 
ured, being 40 millimeters in diameter. They are more scalenohedral in 
habit than those of the foregoing types, the scalenohedrons of the zone 
[1011.1120] being specially prominent. The habit is essentially different 
from any of those figured by Zippe, Hessenberg or Dana and appears to have 
escaped the notice of these writers, probably through lack of characteristic 
specimens. 
Prisms. Both prisms b (1010) anda (1120) are present as well developed 
forms, the latter represented by broad bright faces, much striated parallel 
to the zonal edges of [1011.1120]. 
Pyramids. The pyramid 7(8.8.16.3) noted under type III is here 
present as a form of more pronounced habit, from the faces of which excel- 
lent reflections of the goniometer signal were obtained. 
Rhombohedrons. The positive rhombohedron p. (1011) and m. (4041) 
are here developed in about equal habit, the suppression of the p. planes 
being specially characteristic of the type. Several planes of the positive 
rhombohedron c. (8081) reported by Cesaro’ from Rhisnes but included in 
lists of Irby? and Rogers* as doubtful, appear on crystals 6 and 8, and 
seem to establish the form beyond question. The positive rhombohedron 
t.(16.0.16.1) appeared on five of the eight crystals measured, in every case 
giving measured values of the angle with the cleavage planes which differed 
only slightly from theory. 
The negative rhombohedrons ¢. (0221) v- (0554) and &. (0443) observed 
on type III are here entirely absent but the form 3.(0112) only occa- 
sionally present on the crystals of the previous type is here noted as a 
fairly well developed series of planes. 
Scalenohedrons. The scalenohedrons found upon crystals of this type, 
for the most part lie in the zone [1011.1120], giving to this zone a prominence 
1 Cesaro, G; Soc. Geol. Belg. Ann. 1889. 16:165. 
2Irby, J.R. McD. On the Crystallography of Calcite. Inaug. Dissert. Bonn. 1878. 
3 Rogers, A. F. List of Crystal Forms of Calcite. Sch. of Mines Quar. 1901. 22: 429. 
