PLATE XXIV. 

 Figures magnified 500 diameters. 



PAOE. 

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



Figs. iJ, 3. more common forma and sizes, . 99 



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



Figs. 5-7. XANTHIDIUM CRISTATUM, three forms, . . .100 



Fig. 8. " " end view 100 



Figs. 9, 10. XANTHIDIUM ASTEPTUM, two forms, .... 100 



Fig. 11. " lateral view, . . 100 



