IO 



NEW YORK STATE MUSEUM 



which the natural etchings present on the prismatic planes, em- 

 phasize the twinning habit. Figures 18 and 19 show twin crystals 

 of the second type twinned according to both laws mentioned 

 above. Figure 20 shows a twin crystal of the third type. 



SUMMARY OF OCCURRING FORMS 



aThe scalenohedron (5382) was identified by means of measurements taken with a contact 

 oniometer. 6New. 



CALCITE FROM UNION SPRINGS, CAYUGA CO. 

 In the summer of 1899 Dr John M. Clarke, then State Paleontol- 

 ogist, found at Union Springs some extremely interesting crystals 

 of calcite. Several specimens of these were sent to Yale Univer- 



