88 NEW YORK STATE MUSEUM 
combination, its place being taken by «(4483) a form not hitherto noted 
from this locality but which completes the series of pyramids by supplying 
a logical link in the sequence between (2243) and (8.8.16.3) the former of 
which is present as a highly developed series of planes giving very fair 
reflections. Two negative scalenohedrons, q: (2461), which was also noted 
in types II and IV, and c: (3472), are present as large and well developed 
forms. The positive scalenohedrons K: (2131) and 8: (8.4.12.1) are present 
as well developed forms. A regular and symmetrical roughening was noted 
on the obtuse polar edges of K:(2131) as shown in figure 4 which was 
probably due to some twinning tendency,’ although no twins were observed 
in connection with this type. 7 
The complex zonal relations between the various forms occurring on 
the calcite from Lyon Mountain are shown in the stereographic projection, 
plate 12, and are particularly well illustrated in the combinations of type 
V which includes 11 of the 27 forms observed for the locality. Assuming 
the principle announced by Cesaro”? “that when a crystal of calcite is 
formed around a preexisting crystal, in general the edges of the first crystal 
tend to be replaced by faces which are parallel to them; i.e. a face of the 
new crystal is in zone with two faces of the original one.”” The superposed 
groups of type IV present a striking instance of harmony in zonal relations, 
and indeed the gradual increase in the numbers of forms from type I through 
types III, IV and V shows a close coincidence with Cesaro’s principle. 
1 Tn this connection it is interesting to note that the calculated values of ¢ for (2131) 
and (4261) are the same and that consequently a penetration twin parallel to (0001) 
would bring the superposed planes of these two forms in close orientation and might result 
in a vicinal roughening similar to that observed. 
2Cesaro, G. Les formes crystallines de la Calcite de Rhisnes. Ann. de la Soc. Géol. 
de Belgique. 1889. 16:167. 
