U. S. F. C. 1897. (To fac page 42. , 
Plate IX. 
Valve of Unio in its natural state, and the same with “ blanks " cut out from it. 
" Blanks " as cut ; three upper figures showing inside, three lower showing outside with more or less of the epidermis. 
The same ground but not " centered ” or polished. 
The same centered, i. e., with the central depression made, but not the holes. 
The same with the holes drilled complete. 
A dozen buttons, as fastened on card for sale. 
THE EVOLUTION OF A PEARL BUTTON. 
