PLATE XXIV. 



Figures magnified 500 diameters. 



Page. 

 Fig. 1. XANTHrDiUM ARMATUM, from Mount Everett, Mass., . . 99 



Figs. H, 3. " " more common forms and sizes, . 99 



Fig. 4. " " transverse view of a semi-cell, , . 99 



Figs. 5-7. Xanthiditjm cristat0M, three forms, • . . .100 



Fig. 8. " " end view, . . 100 



Figs. 9, 10. Xanthidittm asteptdm, two forms, .... 100 



Fig. 11. " '• lateral view, . . . 100 



